Water Journal March - April 1997

Volume 24 No 1 March/ Aprll 1997 Journal Australian Wat er & Wastewater Association

CONTENTS From the Federal President .................. ... ............................ Inside front cover From the Executive Director .... .. ......... .................................... ......... ... ......... .... ,. 4 MY Edltorlal Board F R Bishop, Chairman B N Anderson, G Cawston, M R Chapman P Draayers, W J Dulfer, G A Holder M Muntisov, P Nadebaum, J D Parker AJ Priestley, J Rissman

Advertising & Administration AWWA Federal Office General Editor: Margaret Metz Advertising: Lynne Mathias PO Box 388 Artarmon NSW 2064 Level 2, 44 Hampden Road, Artarmon Tel (02) 9413 1288 Fax (02) 9413 1047 Email: awwa@abol.net

Features Editor EA (Bob) Swinton 4 Pleasant View Cres, Glen Waverly Vic 3150 T e1/Fax (03) 9560 4752

Branch Correspondents ACT - Ian Bergman Tel (06) 248 3133 Fax (06) 248 3806 N ew South Wales - Mitchell Laginestra Tel (02) 9412 9974 Fax (02) 9412 9676 Northern Territory - Ken Mcf arlane Tel (088) 924 7363 Fax (088) 924 7161 Queensland - Terry Loos Tel (07) 3224 2146 Fax (07) 3369 4816 South Australia - Peter Martin Tel (08) 8303 8723 Fax (08) 8303 8750 T asmania - D ao Norath Tel (03) 62332 596 Fax (03) 6234 7559 Victoria - Mike Muntisov Tel (03) 9600 1100 Fax (03) 9600 1300 Western Australia - Jane Oliver Tel (09) 420 2462 Fax (09) 420 3178

Water (ISSN 0310 • 0367) is published six times per year: January, March, May.July, September, November by

Australlan Water & Wastewater Inc ARBN 054 253 066

Executive Director Chris Davis Australian Water & Wastewater Association assumes no responsibility for opinions or sratements of facts expressed by contributors or advertisers and editorials do not necessarily represent the official policy of the organisation.

D isplay and classified advertisements are · included as an informational service to readers and are reviewed by the Editor before publication to ensure their relevan ce to the water environment and to the objectives of the Association. All material in Water is copyright and should not be reproduced wholly or in part without the written permission of the Editor.

Subscriptions Water is sent to all members of AWWA as one of the privileges of membership. N on-members can obrain Water on subscription at an annual subscription rate of S39 (surface mail).

OF

VIEW

Engineering Education at the Crossroads ............................ ........ ..................... 3

S Beder CATCHMENT

HYDROLOGY

Cooperative Research with Catchment and Water Managers ....... ............ .... 7

R G Mein WATER AND SALT BALANCE Macaque: Regional Scale Modelling of Water Yleld from Forested Basins ........ 9

F GR Watson, RA Vertessy, RB Grayson, LE Band, TA McMahon Predicting the Water and Salt Dynamics Beneath Eucalypt Plantations ..... 10

RP Silberstein, RA Vertessy, J Morris, L D Connell WATERWAY MANAGEMENT AND EROSION CONTROL Reservoir Sedimentation Data In South-Eastern Australia ... .. .. ...... ............. 11

J Davis, I Rutherfo rd, B Finlayson URBAN HYDROLOGY Modelling Dally Runoff and Pollutant Load from Urban Catchments ........ 16

F H S Chiew, T A McMahon Leaf Litter In Stormwater: A Major Source of Nutrients? ..:........... ........ ....... 18

R A Allison, F H S Chiew Pollutant Removal by Storage: Analysis of Australlan and Overseas Data .. . 19

H P Duncan FLOOD HYDROLOGY Towards Reducing the Uncertainty In Design Flood Estimation ................. 20

P Hill, R G Mein, P E Weinmann Recent Advances In Estimating Extreme Design Rainfalls ......................... 21

PE Weinmann Improvements In Real-time Flood Forecasting ...................... ... ..................... 21

J Elliott WATER Trials of Colllert System ................................................... .... ............................. 22

P W Adcock, C Saint ENVIRONMENT Envlronmental Performance of Sydney's Deepwater Outfalls .................... 29

T Pritchard

•

Sallne Disposal Basins .............. ............ ..... .................. ....... .............................. 35

K Narayan

Federal President Mark Pascoe

POINT

BUSINESS WaterLog ................................................ ....... ...... ...... ........ ........... .......... .... .......... 37

D Cummins WASTEWATER Dewaterablllty of Activated Blosollds ........ ........ ......... .. ....... ........ ................... 39

I H Bane DEPARTMENTS International Afflllates ............. ... .. ................ ................. ......... ........ .. ................. 5 From the Bottom of the Well . ....... .. ...... ........ .. ........... .......... ... . .. .............. .. .. .. ... 2 Meetings .. ......................................................................... ................................... 44 OUR COVER A 3-D radar image of a storm over Brisbane showing areas ofprecipitation. The Commonwealth Bureau of Meteorology, a partner in the CRC for Catchment H ydrology, is evaluating the application of radar to real-time flood prediction. A single radar receiver with a range of 150 km can detect and quantify intense local falls. CR C post-graduate student, Sun X udong, and his supervisor, D r Tom Keenan, are evaluating different methods of usin3 radar data to provide improved estimates of catchment rainfall for use with hydrological models Jor more accurate flood forecasting. Radar image co1trtesy of the B11rea11 of Meteorology Research Centre

Cooperative Research With Catchment and Water Managers Russell Mein Prqfessor R11ssell !vlei11 is Director of the Cooperative Research Centre for Catchment Hydrology, a11d a11 academic i11 the Departme11t of Ci11il Engineering of l\lfonaslt U11ii1e1"Sity. He has long had a strong interest in technology tra11sfer and i11 this arena is best k11oiv11 for his co-authorship of the RORB flood estimatio11 computer package and ef two books on reservoir yield, his Chairmanship of the Advisory Committee for A11stralia11 Rairifall and R1111cift and instmctor for nearly thirty workshops 011 11ario11s aspects ef water engi11eeri11g.

1

Our Mission The mission of the Cooperative Research Centre (CRC) for Catchment Hydrology is "to provide national leadership in improving the understanding of catchment hydrology, its application to land and water management issues, and industry training and education for the benefit of the wider community". Put more simply, the CRC aims to provide an enhanced knowledge base on major land/ water concerns, and to transfer this to industry in effective ways for its use.

for the long period (15-20 years) in hydrology between initial publication and first use by a catchment/water management organisation.

The massive restructuring of State catchment/water agencies in Australia has increased the difficulty in the task of successful and efficient technology transfer. Many organisations now have no research capability, nor even a high level technical group able to monitor scientific journals and adapt published research findings for use in practice.

Nevertheless, management decisions have still to be made, many in areas in which considerable uncertainty still exists. A degree of risk is involved in each decision, with greater risks of being wrong if the knowledge base is inadequate or ignored. Risk without knowledge is dangerous.

On the other hand, researchers thrive on uncertainty; it is, after all, the reason for their endeavours. They seek to fill in knowledge gaps so that,

70% of a management issue is useful now to the catchment manager who has current access to only 50% or less.

Knowledge without risk is useless.

For industry parties to the CRC for Catchment Hydrology, the formal interchange between researchers and managers provides a mechanism for speedy and effective technology transfer. Having developed its research programs with industry, the CRC is expected to identify outcomes of its research relevant to other Dr Mayor, Director General of UNESCO, at International water/catchment agencies in Hydrology Program Meeting, September 1996 The Challenge of Australia (and overseas), and Technology Transfer make them available to this The emphasis on technology wider audience. Perhaps "expectation" eventually, management decisions can transfer is one of the important changes is not a strong enough word here; in the brought about by the Government's be made with a full understanding of major external review of our activities CRC program. It has been standard the consequences. Unfortunately, scheduled for mid-1997, we will be researchers tend not to be risk takers, practice for most researchers to regard judged on the impact we have had (or the publication of research findings in and are often reluctant to share their will have) on Australian practice in expert knowledge of a topic while peer-reviewed scientific literature as the hydrology. Hence, our Technology end point of their work. This left a significant uncertainty remains. This is Transfer Program is at least as imporan attitude this CRC is helping to difficult and uncertain route for the tant in the CRC as our programs of application of new knowledge to overcome, ie making researchers realise research. practice, and has been the main reason that the knowledge they have of, say,

"Risk without knowledge is dangerous; however, knowledge without risk is useless"

WATER MARCH/APRIL 1997

7

CATCHMENT Spreading the Word So, w hat are our plans? H ow do we propose to spread the word, share our knowledge?

The first step has been to identify what have been the outcomes from our research (our products), and which organisations would benefit from this knowledge. Consideration has also been given to the best fo rm in which to "package" the knowledge to enable particular organisations to make use of it. For example, technical reports may be appropriate for some audiences, field demonstrations for others.

T he second step is to make organisatio ns aware of what we are doing and what we have achieved. Raising t he level of awareness is being done in a number of ways. For instance, our newsletter Catchword is sent monthly to more t han 900 people involved in land/ water issues to inform them of CRC research and technology transfer activities. Technical seminars are held at least monthly to provide mo re detailed accounts of particular research projects and outcomes; videos have been made of many of these to widen the audience.

Similarly, a number of field days have been h eld to show, first hand, how some of our research is being conducted and what issues are being tackled. T he selected short articles in this issue of Water are furthe r examples of 'awareness raising', for in themselves they do not have enough technical content for persons wishing to pu t the research findings into practice, but the full reports are readily available from the CRC. The third (and most difficult) step is to 'deliver' the technology to those who want it and in a form suited for their needs. Most of o ur core project work

HYDROLOGY

has produced technical reports; these have been published by the CRC and sold at nominal charge (including through A WWA). For many organisations, this form of knowledge distribution is sufficien t for them to make use of the research results. For others, handson workshops is a more effective transfer format, with the opportunity to question the presenters, and apply the techniques to practical problems during the course. In yet othe r forms o f technology transfer, staff exchanges have been made to allow fo r extended periods of discussion and interchange.

We have also released software packages, and are developing others, to help water/catc hment management agencies implement outcomes of our research. Similarly, the recently published book Hydrological Recipes is another example of the effort by the CRC to package its collective hydrologic knowledge in a form suited for immediate practice.

CRC Water Forum Many issues require water and land managers to consider aspects beyond the limits of catchment hydrology. H ere, I should mention the Water Forum, an association of the CRCs for Catchment Hydrology, Freshwater Ecology, Soil and Land Management, Waste Management and Pollu tion Control, Water Q uality and T reatment. The Forum is now o rganising some technology transfer activities in w hich their co mb in ed expertise is foc ussed on particular (and large) environmental issues. You '11 hear more of these in 1997.

This Feature T he sho rt articles followi ng have been selected from each of the fo u r

HYDROLOGICAL

8

WATER MARCH/ APR IL 1997

Programs which have been operated for the first three years of the CRC. For the next period, th e CRC has sp lit Catchment Water and Salt Balance · Program into a Salinity program and a Forest Hydrology Program so that in future the Research Program structure will be: • Salinity • Forest Hydrology • Waterway Manage ment • Urban Hydrology • Flood Hydrology To these are added t h e equally importan t Education and Train ing Program and Technology Transfer and Commercialisation Programs.

The Board of Management, headed

by Dr J ohn Langford (who is also Executive D irector of the Water Services Association of Aust ralia) together with the wide variety of fulltime and part- time staff from Universities, CSIRO, and the water i ndustry, look forward to effective research and equally effective technology transfer throughout the next th ree years.

Conclusion To conclude, technology transfer is now very much a part of effective research. In catchment hydrology, like other fields, it is a two way process.

Water and catchment managers need regular consultations with researchers to keep track of the current state of relevant scientific k nowledge. On the other hand, researchers need to be aware of th e problems faced by managers, and share their expertise and know- how to help solve them. Such a cooperative approach is the best way to reduce the risks of wrong decisions in environmental issues.

RECIPES

CATCHMENT

HYDROLOGY

WATER AND SALT BALANCE Macaque: Regional Scale Modelling of Water Yield from Forested Basins F G R Watson, R A Vertessy, R B Grayson, L E Band, TA McMahon Abstract

1988) and the Topog model (Vertessy et al 1993, 1995). However, these models A regional scale, process based model of forest hydrology has been developed are difficult to apply to the regional as part of research into water production scale. T opog, due to its computational in managed forests. T he model, named demands, is rarely applied to catchments 2 M acaqu e, allows spatial predictions of larger than 10 km . SDI, on the other cannot accommodate spatial hand, water balance for entire water supply catchments (c. 1000 km2 in area) . It is variation in system properties.

Many key forest variables, such as intended that this model will help improve water supply catchme nt LAI, forest species, precipitation and management influence, are highly management in Australia. variable within a region and hence a regional scale model is required .

Background In the Mountain Ash forests that supply water to M elbourne, water yield depends largely on forest age, with yield declining markedly in regrowth forests followi ng logging or fire (K u cze ra, 1987). This dependence is caused by vari ation in the leaf area index (LAI) of the forest with age and its influence on inte rception and transpiration (Vertessy et al 1994, Watson and Vertessy 1996).

Both the ma nagement and understanding of these fo rests have already benefited from hydrological modelling using the SD I model (e.g. Kuczera,

Do

Macaque

Current status

Macaque (based on RHESSys, Band M acaque has recently made its first et al 1993) employs a ' physically simulations of daily, long term, regional meaningful' representation o f forest scale hydro logy for the Maroondah hydrology, simpler than that of Topog Catchments. Validation against numerbut retaining p hysical representations of ous observed data is in progress. These key hydrological elements. In particular, data include streamflow, canopy intersoil moisture dynamics are based on a ception, transpira tion, soil moisture statistical distribution function rath er storage, evaporation, and water table than explicit sub-surface flow routing. levels.

T his places less data demands on the model and enables it to be rapidly References applied at a daily time step to entire Band L E, Patterson P , Nemani R , and Running

nYTI

D1 12 13 14

nYTI

1984 March average daily recharge.

. .,

nYTI

nYTI

' \,

...

..,. ¡.' ..-

nYTI

Is 16 17 le 19 l 10 I>

nYTI

nYTI

nYTI

nrn

nYTI

nrn

10

Metres nYTI

0

2000

4000

basins for periods of more than 100 years.

Inpu t to the model (such as future w ildfi re scenarios) and outputs (such as streamflow) are modelled as spatially variable phenomena. Spatial maps of water balance can be produced. For example, Figure 1 shows predicted recharge to groundwater fo r summer and winter over a large area. Spatial predictions of this kind can be used to ide ntify key water production areas or areas sensitive to disturbance.

6000

8000

10000

Figure 1 Spatial predictions of recharge to groundwater for th e Coranderrk catchment (18 km 2 ) fo r both wet and dry months

S (1993) Forest ecosystem processes at the watershed scale: incorporating hillslope hydrology. Agric. For. Meteorol., 63:93-126.

Kuczera G A (1987) Prediction of water yield reductions followi ng a bushfire in ashmixed species eucalypt forest. J. Hydro/. , 94:215-236 .

Kuczera G A (1988) T he soil dryness index screamflow yield model: An overview of its development and capabilities. Hydr. & Wac .

R es. Symp., ANU, Canberra, 1-3 Feb. 1988, Preprints of Papers, 103-107.

Vertessy RA, Benyon R , and Haydon S (1994) Melbourne's forest catchments: Effect of age on water yield. Water, 21(2): 17- 20.

Vercessy R A, H atton T J, Benyon R J, and Dawes WR (1995) Long term growth and water balance predictions for a mountain ash (Eucalyptus regnans) forest catchment subject to clearfelling and regeneration. Tree Pl,ysiology, 16:221- 232.

Vertessy RA, Hatton T J, O'Shaughnessy P J , and Jayasuriya M D A (1993) Predicting water yield from a mountain ash fo rest catchment using a terrain analysis based catchment model.]. H ydro/., 150:665-700.

Watson F G R and Vertessy R A (1996) Estimating Leaf Area Index from Stem Diameter Measurements in Mountain Ash Forest. Report 96/7, CRC for Catchment H ydrology, Melbourne.

WATER MARCH/APRIL 1997

9

CATCHMENT

HYDROLOGY

Predicting the Water and Salt Dynamics Beneath Eucalypt soil salt accumulation, will be fo recast Plantations for sites w hich may have different soil RP Silberstein, RA Vertessy, J Morris, L D Connell Ove r 200,000 hectares of the Murray Irrigation Area are affected by shallow saline watertables, of w hich at least 30% is unsuitable for groundwater pumping and re-use due to the low permeability of the soil or the salinity of the water. The establishment of plantation s has been identified as a possible alternative strategy to maintain commercial viability of the region. The _feasibility of this strategy depends on the achievable growth rate of the trees (closely related to water use), the extent of the beneficial effect of the trees on the surrounding agricultural land through watertable control, and on the sustainability of the system . The sustainability may be limited by the potential for salt accumulation beneath the trees through concentrated water up take.

An ecohydrological m odel (TOPO G D ynamic) has been developed to predict the plant growth and th ree di m en sional wa ter and salt balances of heterogeneous catchm ents.

The model uses Richards' equation fo r vertical m oisture flow, in multilayered soils, D arcy's Law fo r lateral saturated the convec tio n-di spersio n flo w, equatio n for solute tra nsport , and evapo tran spiratio n base d o n the Penman-M onteith model. Soil water extractio n is thro ugh a distributed root system from the multilayered soil, and there is water interchange with the underlying aquifer system . A physiologically based plant growth module allocates carbon to roo t, stem , branch and leaf compartments, dependent on water, nutrient and light availability, ambient temperature, and soil salinity.

Thus plant grow th and water use and soil-water solute dynamics are closely linked.

The modelling study 1s b eing complemented with field observations of watertable levels and the development of salinity levels within the root zone of a small plantation (-2ha) of three species (established in 1977), surro unded by irrigated pasture. A network of shallow and deep piezometers was es tabli sh ed and ha s b een monitored for level and salinity. T wo years ago m onitoring at the site was significantly upgraded , with digital loggers installed in 12 piezometers , heat pulse sapflow meters installed in 6 trees and m oved eac h week , unsatu ra ted zone soil moisture and salinity, canopy leaf area and throughfall , and installa10

WATER MARCH/ APRIL 1997

tio n of an automatic meteorological station. The data show that after an initial period of drawdow n, followed by a period of relatively stable level, the watertable under the plantation may have begun to rise, coincident with a fall in leaf area, and reduction in growth rate.

The model is being tes ted by hindcasting the grow th and water use of the plantation , and soil salinity developm ent. The model is then to be used to forecas t the fu ture of thi s plantation under current m anagem ent (i. e. no irriga tion direc tly) o r m odified practices. The impact of rising salinity levels is of particular concern , as the plantation is likely to reduce its water consumption further m response to this stress.

The model will then be applied to similar plantations for sites at w hich we do no t have adequate fi eld data.

Plantation water use and grow th, and

and watertable characteristics. A range of likely plantatio n and watertable outcomes will also be examined fo r diffe rent sites with diffe rent planting and management stra tegies.

Authors Fred Watson is a R esea rch Scholar, Dr Rodger Grayson is a Senior R esearch Fellow, and Prof Tom McMa hon is

Professor of Environmental Hydrology at the University of Melbourne. Dr Rob Vertessy is a Senior R esearch Scientist at CSIRO Division of Land and Wate r, Ca nberra, and is Proj ect leader, A2.

(Predicting Wate r Yield). Prof La rry Band of the University of Toronto is an associate of the CR C CH. Richard SIiberstein works with Dr. R ob Vertessy at the CSIRO Division of Land and W ater, Canberra. Dr Jim Morris is with the Victorian D epartment of Natu ral R esources and E nvironment, Dr Luke Connell, at Monash University, is Proj ect Leader A 1 and A5, dealing with high water table areas.

atmospheric inputs (radiation, humidity, temperature, windspeed, rainfall) interception

evaporati on

t re charge

lateral flow -

Figure 1 Processes in cluded in TOPOG_Dynamic mod el Water Content

/

11:zzz==izzzl ______ ~

Root Density

Mo;, iure Content

Salt Concentration

&.L Soil Surface

- • • Winter Profile

--.-·- - - - - -

-

Summer Proll!e

-

- Winter Watertable

E22J Summer Watertable Root Density

Soil Water Salt Concentration

Figure 2 TOPOG_Dynami c modelling results showing the interconnections betwee n the soi l moistu re, sa lt and root dynamics

CATCHMENT

HYDROLOGY

Reservoir Sedimentation Data in South-Eastern Australia reservoirs, although at times surveys were not completed or documented if the initial results demonstrated minor Abstract (< 5,000 Ml) in N.S.W. and South or negligible sedimentation . D etailed Some smaller reservoirs in Australia Australia (e .g. Morse and Outhet 1986, and reliable survey information was have filled to the brim with sediment, Moore 1990). However, none of the obtained from files of the R WC for rendering them worthless. Larger reser- large r reservoirs 111 so uth-eas tern eight Victorian reservoirs (see list of voirs have not suffered the files in the bibliography) same fa te, which is due, in and the map (Figure 1) .

E Lake Hllne A Cairn Curran ReeerYolr part, to the large capacity of The data for each of the F MeH:on R111ervol r 8 Elldon Reservoir the reservoirs in question, as rese rvoirs are presented G Pykes Creek Reservoir C Glenmaggie R11trvok 0 Laan.coorie R1Mrvoir H Roddands ReletVOir well as the lower sediment below in graphical form yields produced by the (Figures 2 & 3). larger ca tchments. Thi s For a number of the paper reviews sedimen t reservoirs shown in Figure E~ deposition into eight large 2, there is more than one Victorian reservoirs, sediment yield given, D 8 A H showing that sediment indicating ' that more than yields are typically less than one survey was carried out S0t.km -2 .yr -l into large at that particular reservoir.

N reservoirs. However, in T emporal sediment yield t some circumstances sediment patterns are illustrated in o soi.m L--J yields to a reservoir can be Figure 3, where sediment high. Enhanced yields are yield data for four reserFigure 1 Location of RWC reservoirs with sed iment survey data ca used by in-stream gold voirs is graphed over time. mining, run-off following The data presented in fires in steep catchments , run-off from Australia appear to have recorded the two figures indicates two things. unu sually erosive ca tchments, and substantial capacity losses in the past The first is that sediment yields from finally , from sand slugs, from historic (e.g. AWRC 1969 , Outhet 1991). In the eight Victorian reservoir catchcatc hment erosion , moving down this pap er sedimentation rates and ments have, for the most part, been less stream networks. sediment yields for eight Victorian than 50 t.km-2 .yr-1 . However, four of reservoirs are investigated to determine the catchments have produced sediment Introduction average sediment yields, but also yields in excess of 50 t.km- 2 .yr-1, T here are over seventy reservoirs in circumstances in which sediment yields sustained over varying periods of time.

Victoria with walls over Sm high , with can be unusually high .

The RWC (RWC file 60/40489), and researchers such as Walling and at least forty-two of these being defined W ebb (1983), designate sediment yields as large storages (DWR 1989). With Reservoir Sedimentation Data the recent restructuring of the water Until its demise in 1995, the Rural ofless than 50 t.km- 2 .yr- 1 as low. Thus, the R WC data indicate that sediment industry in Victoria, responsibility for W ater Corporation of Victoria (R WC) many of these reservoirs is passing to was responsible for managing most of yields from large catchments in Victoria and south-eastern Australia are typically new organisations. An issue that may the State's large water supply reservoirs. concern these new owners is sedimen- The R WC monitored reservoir low. Sediment yield of this magnitude tation in their water storages. sedimentation in many of their reser- is also supported by data from large reservoirs in N.S.W. (Outhet 1991).

Reservoir sedimentation can prove to voirs using the Rangeline T echnique.

It is important for reservoir managers be an extremely costly problem. Not This technique involves surveying preonly does sedimentation reduce water defined "silt lines" within a reservoir, to appreciate that high catchment to determine the depth of sediment erosion rates seldom transla~e into high storage capaciry, but it can also reduce water quality and damage outlet works, rates of reservoir sedimentation in large depo sited in the re servoir b etwee n seriously impacting on the useful life surveys. This volume could then be SE Australian catchments. It is well and economic viability of a reservoir converted into a sediment yield per- known that ero sion rates in many (ICOLD 1989, M eadowcroft 1992) . unit-catchment area.

Victorian catchments have been high Serious sedimentation problem s have Since the 1930s silt-lines have been since European settlement, with been recorded in small reservoirs surveyed on many of Victoria's larger dramatic gullying and erosion of the

J Davis, I Rutherfurd, B Finlayson

WATER MARCH/ APRIL 1997

11

CATCHMENT

HYDROLOGY

catchment surface. However, most of Although the sediment yield to sedimentation as moderate.

What other areas of the state were the sediment that has been liberated by Laanecoorie Reservoir was not excesaffected by similar high sediment yields this erosion is deposited again, usually sively high, the small capacity of the quite high in the catchment. Only a reservoir resulted in a significant impact from mining? Mining records show that dredging and hydraulic mining on the reservoir. small proportion of the sediment makes were not only used in the Castlemaine High sediment yields associated with it into the larger rivers and through the District (SAB 1906- 1917), but in fact such mining practices occurred because catchment (eg. Melville and Erskine, mining sediment was not stored, even other parts of t he State were also 1986; Rutherfurd and Smith, 1992).

Having said this, there are some temporarily, in the upper catchment. affected. The peak period for instream mining was from 1907-1909 (SAB Instead the effluent was pumped cases in which sediment does get into 1913) and data for 1907 indicates that directly into the main tributaries. larger streams and so into reservoirs.

Examples of streams upstream of the districts of Beechworth and Four of the reservoirs shown in Figure Laanecoorie Reservoir, where such Ballaraat were similarly affected (SAB 1 have experienced unusually high mining took place, are the Loddon 1908). The Beechworth District may sedimentation rates. The catchments that have produced sediment yields River (upstream of Newstead), be taken as a worst case, with 50 dredgCampbells Creek, Fryers C reek and ing and sluicing operations in the exceeding 50 t.km- 2 .yr-1 in the past are: district in 1907. (a) Laanecoorie Reservoir catchment; Forest Creek (Forbes 1950). The A 1913 Sludge Abatement Board discharge of mining effluent from these (b) Pykes Creek Reservoir catchment; sites continued for a number of years Inquiry reported many instances of (c) Melton Reservoir catchment; and and the resulting sedimentation serious stream and floodplain siltation (d) Lake Eildon catchment.

The high sedime ntation rate in each problems were further exacerbated by throughout the Beechworth area. of these reservoirs occurs as a sudden an increase in discharge from the Upper Sandy C reek, a tributary to the Mitta increase in yield, (ie . a spike of Loddon catchment as the result of Mitta River with a catchment area of approximately 155 km 2 , sediment), after which the was the subject of extenrates fall to the low levels sive dredge mining operarecorded for other resertions. The SAB reported voirs (ie. less than 50 t.km....>, 500 that in the Sandy Creek 2.yr-1) (Figure 3). Each of 'l~'e 400 a these reservoirs experiences valley, which runs from X :!;!. the confluence of Sandy high sedimentation rates for 300 Creek with the Mitta a different reason. These ai Mitta River to a point 3 reasons include gold > 200 a C miles (5 km) upstream, a mining, fire, and unusually GI X E 100 deposit of m111111g erodible catchments. In A 50 t.km-2_yr"1 ~ ---- - -- -- -:.J;,.-aJj ·- ~- - ---]l"' · ·· · ---most cases these processes sediment 4 feet (1.3 m) GI Cl) 0 deep had been laid down have to b e combined with a (SAB 1915), which is 100,000 1,000 10,000 steep catchment in order to 100 2 equivalent to - 7 .2 million move sediment directly into Catchment Area (km ) m3. reservoirs.

Most of this sediment a Pykes Creek A Melton :: Laanecoorie Gold Mining deposit is now under the oRocklands xEildon •Hume Hume Reservoir, but was Laanecoorie Reservoir ~ Glenmaggie • Cairn Curran deposited before the reserhas suffered dramatic voir was built. We can sedimentation because of conclude that the same is gold mining. The reservoir Figure 2 Sediment yield vs catchment area for eight large true for most areas affected was built on the Loddon Victorian reservoirs by mining in Victoria.

River in 1891. At this time Most in-stream mining a substantial amount of occurred before the reservoirs were diversions from the Campaspe River mining was still continuing in the built, or in catchments without large basin (Sludge Abatement Board, region, although it had declined from reservoirs. Therefore, whilst mining SAB,1910). the initial gold rushes of t he 1850s and An increasing awareness of the can have a dramatic impact on reservoir 1860s (Bowan 1982). By the early effects of mining had led to the formacapacity, the impact appears to have 1890s most of the alluvial gold had been short-lived (eg. Laanecoorie), and tion of the Sludge Abatement Board been taken and the m iners that most of the impact predates reservoir (SAB) in 1905, whose brief was to remained were having to use more construction. control these environmentally damagheavy-handed methods of extraction, Nevertheless, in-stream mining is an ing practices. According to R WC files such as dredging and hydraulic mining. example of an activity that can lead to the SAB was responsible for eventually In hydraulic mining, the miners used reducing the rate of sedimentation of rapid reservoir sedimentation because pressurised water jets delive red by pipes the sediment by-passes natural the reservoir (Green 1953). Surveys or hoses to wash- out alluvial deposits sediment stores in the catchment. conducted after the initial reservoir for the purposes of sluicing (Shakespear survey demonstrated a significant etal 1887).

Dramatic Catchment Erosion reduction in the rate at which sediment One of the consequences of dredgwas entering the reservoir. The final Both Melton and Fykes Creek resering and hydraulic mining in the survey in 1962, 30 years later, demonvoirs have had high sedimentation rates Loddon catchment was the sedimentastrated a further reduction of only 5% because of a combination of unusually tion ofLaanecoorie R eservoir. Over its erodible catchments, and erosion along first 41 years of operation Laanecoorie in the rese rvoirs capacity, with sediment yield declining to 10 t.km- 2.yr-1 . stream lines. Melton R eservoir, which lost 53% of its capacity (sediment yield The R WC then listed the rate of was built on the Werribee Rive r in of 50 t.km-2 .yr- 1 ) to sedimentation.

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WATER MARCH/APRIL 1 997

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HYDROLOGY

1916, and Fykes C reek Reservoi r, the total loss of capacity at 19 .6% above the reservoir. H en ce, although constructed on Fykes Creek in 1911, (sediment yield of70 t.- 2 .yr-1), with just the 1940s was a p eriod of high erosion were enlarged in 193 7 and 1930 respec7.7% lost over the 33 years since the potential across Victoria because of tively. Both catchments arc w ithin the 1945 survey (sediment yield of 50 drought, rabbits, overgrazing etc., the Werribee Basin whic h , earlier this t. km-2 .yc 1). The most recent work on Melton and Pykes C reek catchments century, was notorious for its eroded M elton R eservoir by the R WC suffered from unusually severe erosion. condition. suggests that there has been no signifiThis was because of the unusual characThe period 1936- 1950 saw a combicant sedime ntation of the reservoir ter of the soils of the catchment. The re nation of environmental fac tors, acting since 1960 (RWC file 80/2983) . are arguably no other catchments in throughout th e State, that induced in Pykes Creek Victoria that are so susceptible to D eposition erosion. There was a prolonged dry R eservoir occurred in very similar erosion, and suc h erosi on can be spell, a p oor rural econ omy (that led to circumstances to the sedimentation of considered extraordinary. poo r land management practices such as Melton R eservoir. In 1945 the Pykes overgrazing), and a severe rabbit plague .

Creek catchment was hit by a storm Sedimentation Following Fire All of this left areas already vulnerable which carried a con siderable quantity of In certain circumstan ces, fire in a to degradation, such as the W erribee silt and gravel dow n into the storage catchment can lead to dramatically Basin, exposed to e rosion. This resulted (Murley 1981). A survey was carried increased sediment yields, and reservoir in landslips and landslides across the out at the reservoir in 1945 and it was dep osition. This is the case in the catchment (Forbes 1948) whic h reported that the reservoir had lost 7% Eildon R eservoir. The first impoundprovided the main trunk streams with a of its original capacity (sedime nt yield ment on the Goulburn River was built substantial source of sediment. of 430 t.km- 2 .yr- 1). Another survey was in 1927, forming Lake Rildon. The fi rst Consequently, w h en seve re rainfall carried ou t in 1960, 15 years on, which survey of Lake E ildon was carried out events combined with such in 1930, and indicated that conditi ons, catastrophic the storage had lost just resulted. sedime n tation 0.2% of its storage capacity -A- Eildon --- Laanecoorie Such a "sedimentation" to sedimentation ove r 3 -c- Pykes Creek event was recorded twice ~ Melton years. The 1939 survey in the Melton catchment showed a loss of0.5% over 450 and once in t he Fykes 9 years (sediment yield of70 -.... 400 Creek catchment ove r this ~ t.km- 2.yr-1) , however the p eriod. ::i:, 350 surveys that followed illusN The first eve nt in the trated a dramatic increase ~ 300 catchment M elton in the rate o f siltatio n.

6 250 occurred in J anuary 1941, Between 1939 and 1940 "O 200 ..... when a seve re thu ndera, the rate reached 0.4%.yr- 1 150 sto rm struck p art of the (sediment yield of 330 W erribee River Basin. The "O 100 t.km-2 .yr- 1 ) before Q) event was significant dropping back to 0.2%.yr-1 50 because: i) it produced the (sedime n t y ield of 130 highes t maximum m ean t.km- 2 .yr-1 ) over 1940/41 1880 1900 1920 1940 daily flow recorded to that 1980 1960 diminishing to and Year time; ii) it occurred m undetectable levels thereand iii) it summe r; after.

Figure 3 Temporal sediment yield patterns for four of the followed a p eri od of The ri se in sediment Victorian reservoirs drought (1936, 1937, 1938 yield to the reservoir & 1940) (see SRWSC followed the burning of 1984). Prior to the storm the reservoir found that in that time the reservoir about half of the catchment in 1939, was almost empty, h oweve r, the had lost only a further 2% of its capacleaving large areas of the ground surface sediment lade n runoff from the catch ity, the sediment yield declining to 220 unprotected from erosi on . H eavy ment filled the storage (23 x 10 3 Ml t.km-2 .yr-1 . According to RWC files no winter rains on these vulnerable areas, capacity) in only 36 ho urs (R WC file more surveys have been completed at seve ral months later, led to large 80/2983). this reservoir and the rate of siltation of quantities of sediment being detached A similar "sedimentation" event the storage is considered to be moderand transp orted to the reservoir Ooseph occurred just over 4 years late r in ate (R WC 80/2983).

1953).

February 1945 w hen, in similar The environmental conditions The Forests Commission observed circumstances, a storm raised the level between 1935 and 1945 were such that extensive and serious erosion, accomof the reservoir from 18 ft (5.5 m) to 33 the erosive nature of the Werribee panied by 'siltation in the streams', as a ft (1 0.1 m). This event carried large Basin was aggravated, resulting in catasresult of heavy winter rains on parts of quantities of silt and debris down into trophic sedimentation events in the the Victorian Highlands devastated by the reservoir, killing fi sh and eels Pykes Creek and M elton R eservoir the 1939 fires (Galbraith 1940) . D espite (RWC file 80/2983) . catchments. The sedimentati on of the spike of sediment from the fires, The 1945 survey showed that the M elto n Reservoir can be mostly Eildon has still not lost a significant reservoir had lost 11. 9% of its capacity attributed to the highly erosive nature proportion of its capacity. between 19 16 and 1945 (sedime nt of the Miocene sediments in the The R WC estimated that between yield of 90 t.km-2 .yr- 1 ) and this was Parwan Valley (Forbes 1948). Whereas 1927 and 1953 the reservoir had lost attributed primarily to the 1941 and the sedimentation of Pykes Cree k just 1.26% of its storage capacity. The 1945 flood events (Forbes 1948). Since Reservoir was mainly related to severe most recent surveys, th e latest being in that time two more surveys have been landslips (Forbes 1948) that feed 1982, indicate that for the enlarged completed, the last in 1978, which put sediment dire ctly into streams just storage (now 3,390 x 10 3 Ml) reservoir

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WATER MARCH/APRIL 1997

13

CATCHMENT This is shown by the declining sediment yields in even these extreme cases.

Other high sediment yields to reservoirs relate to a specific erosion process.

Intense fires, followed by intense storms, can lead to dramatic erosion and sedimentation, but only if the catchment is particularly steep. Fire would certainly be the major sedimentation threat to reservoirs that have forested catchments in Victoria. Several forested Melbourne Water reservoirs would fall into this category. The 1939 fires led to considerable loss of capacity in these valuable storages. Other examples of high sediment yields are related to instream gold mining. Much of this impact predated reservoir construction, and these mining practices no longer occur. Nevertheless, in-stream mining is an example of an erosion process that sedimentation because leads to sediment is washed directly into the stream channel.

A final category of risk for reservoir owners is from the sediment (mostly sand) already stored in the stream network, and moving as 'slugs' down the river channel. A large volume of sand can be stored in the channel, and this will eventually move into the reservoir over the next century.

To conclude, lost reservoir capacity through sedimentation is not a major problem in large Victorian reservoirs.

However, there are some specific circumstances in which sediment yields to reservoirs can be high. These circmnstances are outlined in this article.

Reservoir owners can assess the risk to their own reservoirs by considering these examples. We are presently develConclusions opmg simple tools that reservoir Although catchments in SE Australia managers can use to assess the sediment have suffered from greatly elevated yield potential of their reservoir. sediment yields over the last 150 years, much of this sediment has either gone References through the stream system before reser- Australian Water Resources Council (1969) voirs were built (eg. in the case of Sediment sampling in Australia. Australian mining sediment), or is stored high in Water Resources Council Hydrological Series No. 3. the catchment and docs not reach large reservoirs. Thus, in general, sediment Bowan, K.G. (1982) Minerals. In: Duncan,J.S. 1982. Atlas of Victoria. Victorian yields from large Victorian catchments Government Printing, Melbourne, Victoria. are low (typically less than 50 Davis, J.A. (1996). Catchment Management for The Impact of Sand Slugs t.km- 2 .yr- 1) and most reservoir owners the Control of Sediment Delivery: the Case of the Eppalock Catchment, Victoria.

In the preceding sections we have can use this value to estimate the Unpublished PhD Thesis, Department of discussed the fact that there are many maximum sedimentation rate of their Civil and Environmental Engineering, natural stores of sediment in catchments storage. However, there are certain University of Melbourne. that limit the movement of sediment circumstances in which sediment yields Department of Water Resources (1989). Water Victoria: An Environmental Handbook. into reservoirs. Sediment will only to reservoirs have been much higher Victorian Government Printing Office, on move right through the stream system if than this low rate. Such yields have behalf of the Department of Water the sediment can by-pass sediment occurred for a variety of reasons. Some Resources, Melboume, Australia. catchments have special geological stores (cg. via in-stream mining or in Forbes, I.G. (1948) Erosion on the Melton Catchment. State Rivers and Water Supply particularly steep catchments). characteristics that make them particuCommission, Melbourne.

However, some of these sediment stores larly susceptible to severe erosion, Forbes, I.G. (1950) The Catchment of the Cairn Melton and Fykes examples being the are not permanent, they only slow Curran Reservoir. State R..ivers and Water down the movement of sediment into Creek Reservoir catchments. Present Supply Commission, Melbourne. the reservoir. A good example of this land management practices almost Galbraith, A.V. (1940) Forests in relation to water conservation and erosion. In: preclude such high sediment yields. process is 'sand slugs'.

sedimentation is of the same magnitude as the errors related to the survey technique.

The Watts River catchment provides a second example of the response of a Victorian Central Highlands catchment to the 1939 fires. A small part of the catchment was burnt-out by the fires and the winter rains that followed activated severe sheet erosion, resulting in the siltation of Maroondah Reservoir. Despite the size of the area affected more sediment entered the reservoir as a result of this erosion than had accumulated in the previous 10 years (Kelso 1940).

During the Ash W cdnesday bushfires in 1983, 33 ha. of a 35 ha. catchment at Millgrove, near Warburton in Victoria, was completely burnt out. The bushfire followed a drought and so the hydrophobicity of the soil was enhanced. These factors combined with steep slopes (20°-28°), and an intense thunderstorm in the catchment six days after the fire passed through, resulted in mudflows and substantial erosion. The resulting sediment yield was estimated to be 770 t or 2200 t.km- 2 from one storm (Leitch et al 1983). These examples contrast with the response of the nearby Wallaby Creek catchment after a bushfire in 1982. Drought conditions had prevailed prior to the fire, so soil hydrophobicity was well developed.

The entire catchment was burnt out but not all of the tree crowns were destroyed and consequent leaf fall following the fire provided some surface protection. The topography was gently undulating and rainfall totals following the fires were low (Ronan 1986). There was not a significant erosive response in this catchment and the author mainly attributed this to the gentle slopes and low, post-fire, rainfall totals.

This evidence suggests that bushfires and extreme rainfall events can produce greatly elevated sediment yields over several years. However, this sediment is only likely to move through a stream network, and into a reservoir, if the catchment is steep.

14

WATER MARCH/APRIL 1997

There are many streams around Victoria that have filled with sand as a result of gully and sheet erosion in the upper catchment. Most of these streams have a catchment that is dominated by granite. Thus, eroded sand is moving gradually through the stream system as a series of 'slugs', and it is not unusual for these slugs to reach reservoirs. A small weir on Mollisons Creek, 100km north of Melbourne, Victoria, for example, periodically fills with sand from erosion of the catchment that occurred almost a century ago. The sand moves into the reservoir as sand slugs, and these have to be cleaned out of the reservoir at regular intervals to maintain water supply to the township of Pyalong. Water supply to Pyalong has to be rationed in most summers because of the sand.

In another example, repeated silt surveys of Eppalock Reservoir show that the sediment yield to the reservoir has declined from all tributaries to the reservoir except one. The Coliban River delivers sand to the reservoir at a relatively constant rate, and the fact that many of the tributaries to the Coliban are filled with sand indicates that this trend will continue for some time (Davis 1996). There is no question that such sand slugs will be the major source of sediment to Eppalock in the future.

Reservoir owners looking to assess whether their reservoirs may be likely to suffer from sedimentation due to sand slugs, should first look at the catchment geology because granite catchments are particularly susceptible to this type of sedimentation problem (Rutherford, 1996).

CATCHMENT

HYDROLOGY

Victorian Institute of Surveyors 1940. Soil jo11rna/ of Soil Conservation, N.S.W., 42 (1): E rosion in Victoria. Department of Lands 11-14. and Survey (Victoria), Melbourne, Victoria.

Murley, K.A. (1981) Outlet works for dams, !COLD (1989) Sedimentation Control of Part 1. Siltation of reservoirs. Paper delivReservoirs - Guidelines, Bulletin 67. ered ac the Technical Session of the 21st !COLD, Paris.

AGM and Study Tour, Toowoomba, 1981.

Joseph , O.F. F. (1953) Siltation of reservoirs: Outhec, D.N. (1991) Sedimentation in Variable Eildon surveys analysed . Aqua, November, Reservoirs New South Wales. PhD. Thesis, 1953: 19-23.

School of Earth Sciences, Macquarie Kelso, A.E. (1940) Erosion in relation to urban University, February 1991. water supply. In: Victorian lnscicuce of R onan, N.M. (1986) Water Supply Catchment Surveyors 1940. Soil Erosion in Victoria.

Hydrology Research-The Hydrological Department of Lands and Survey (Victoria), Effects of Fuel R eduction Burning and Melbourne, Vicco1i a.

Wildfire at Wallaby Creek. MMBW, Leitch, CJ., Flinn, D.W. and van de Graaff, Report No.: MMBW-W-0015.

R.H.M. (1983) Erosion and nutrient loss Rural Water Commission of Victoria (RWC) resulting from Ash Wednesday (February files: 1983) wildfires: a case study. A11stralia11 - 60/3089 Cairn Curran Reservoir, Forestry, 46 (3): 173-180.

R eservoir Siltation.

Meadowcroft, l. C., Beccess, R. and Reeve, C.E. - 60/40489 General File, Reservoir (1992) Numerical modelling of reservoir Siltation. sedimentation. In: Parr et al. (eds.) 1992.

61/ 2965 Spring Gully Reservoir, Water Resources and Reservoir Reservoir Silcation.

Engineering. Proceedings of the 7th - 61/3452 Lauriston Reservoir, Reservoir Conference of the British Dam Society, Siltation.

U niversity of Sterling, June 1992, Thomas - 61 /3455 Upper Coliban Reservoir, Telford, London, p.: 211- 218.

Reservoir Siltation.

Melville, M. D. and W. Erskine (1986) - 61/3475 Malmsbury Reservoir, Reservoir Sediment remobilization and storage by Siltation. discontinuous gullying in humid southeast- 68/ 1690 Lake Eppalock, Reservoir ern Australia, Proc. I.A.H.S. Symposiu m, Siltation .

Albuquerque, NewMexico.

- 80/ 2983 Melton R eservoir, R eservoir Moore, S. (1990) Land use changes and erosion Siltation. rates in the Pekina catchment, Sou th Rutherfurd, I. D. and N. Smith (1992) Australia. A11stralia11]01mial of Soil a11d Water Sediment sources and sinks in the catchment Conservatio11 , 3 (2): 26-30. of the Avoca River NW Victoria, Report to Morse, RJ. and Outhet, D.N. (1986) Sediment D epartment of Conservation and Natural management on a total catchment basis.

R esources.

Rutherford, I. (1996) Sand-slugs in south ease Australian streams: origins, distribution and management. First National Conference on Stream Management in Australia, Merrijig, February, 1996.

Shakespear, R.H., Walker, A.F. and Rowan, J. (1887) Report of the Board Appointed by H is Excellency the Governor In Council to Inquire into the Sludge Question. In: Victorian Parliamentary Papers, 1888. John Ferres, Government Printer, Melbourne, Victoria.

Sludge Abatement Board (SAB) (1906- 1917) Report of the Sludge Abatement Board for 1905-16. In: Mines and Water SupplyAnnual Report of the Secretary, Minister of Mines and Forests for Victoria.

State Rivers and Water Supply Commission (SRWSC) (1984) Victorian Surface Water Information, Volumes 1-4. State Rivers and Water Supply Commission of Victoria, Armadale, Victoria.

Walling, D.E. and Webb, B.W. 1983. Patterns of sediment yield . In: Gregory, K.J. 1983.

Background to Palaeohydrology. W iley & Sons, London.

Authors Dr Ian Rutherfurd, of Monash Un iversity, is project leader, B2. Assoc.

Prof. Brian Finlayson is in the D epartment of Geography and Jennifer Davis is a PhD student in the Department of Civil and Environmental Engineering at Melbourne University.

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URBAN HYDROLOGY Modelling Daily Runoff and Pollutant Load from Urban this reason, the imp ervious and perviCatchments in the soil stores and the potential rate. ous areas are modelled separately. The F HS Chiew, TA McMahon Introduction Urbanisation leads to higher runoff and pollution loads. Estimates of runoff and pollution loads are required to evaluate options for managing pollutants in urban waterways and receiving waters. This paper describes a daily urban runoff and pollutant load model d eveloped by the CRC for Catchment Hydrology (CRCCH) .

Runoff Model

The evapotranspiration demand is satisfied first from the larger store, therefore indirectly allowing for some redistribution of water between the two stores.

Ratlonale for the Model Models for estimating urban runoff have been available for several decades.

H owever, the better ones appear to be too complex in representing what is quite a simple process. There has also been development in our understanding of the rainfall-runoff process. In addition, the model should facilitate the simulation of pollutant loads, in particular the water quality associated with the different runoff components.

Most of the runoff in urban areas come from impervious surfaces. For

key variable for estimating urban runoff is therefore the fraction impervious area. This can be determined fairly accurately from aerial photographs or rainfall-runoff plots of small events, if good event data are available (see Boyd et al 1993).

C onceptual rainfall-runoff models, which have been applied successfully to rural areas, can be easily adapted to simulate runoff from pervious urban areas. Recent CRCCH studies have compared the application of seve ral conceptual hydrologic modelling approac hes (see Chiew et al, 1993, 1995; and C hiew and McMahon, 1996). One of the main conclusions is that a simple conceptual approach is sufficient to estimate urban runoff adequately. To allow better interpretation of the model results and increase the potential for using the model in ungauged catchments, the CRCCH model attempts to mimic the actual catc hment processes . The pervious area runoff model is based on the partial area saturation excess runoff gene ration, a concept favoured by the newe r hydrologic models, particularly for temperate and wet humid areas (see Z hao, 1992; and R obinson, 1993.).

Figure 1 shows the structure of the runoff model. The catchment consists of impervious area (impervious surfaces directly connected to drains) and pervious area (remaining parts of catchment) .

For the impervious area, after the rainfall amou nt has exceeded a small thresh old, all the rainfall b ecomes runoff.

The pervious area of the catchment is modelled as two separate parts with different storage capacities (related to 'effective' soil d epth). T he first h as a smaller storage capacity and represents parts of the catchment which saturates easily. The second represents the remainder of the catchment with a greater soil storage capacity. Surface runoff occurs w h e n the Figure 1 Structure of runoff model storage capacities are exceeded (when satu ration ~ occurs).

Water from the soil stores Roads recharges a groundwater High Urban store when the storage Residential exceeds a certain am ount "' ;:) ('field capacity'). Recharge is "0 Industrial C ('I ,,............. calculated as a parame ter Commercial ..;i (which mimics the hydraulic Agricultural co ndu ctiv ity) times the Forest amount that the storage exceeds the 'field capacity'.

1 10 100 0. 1 Baseflow from the groundConcentration (m!V'L) water store is simulated using a linear recession.

Figure 2 Example total nit rogen EMCs from urban studies (mean + Evapotranspiration is depenone standard deviation) (Other charts available for TSS, TP, Pb, Zn, dent on the amount of water Cd, Cr, Cu, Ni, COD, BOD, oil) ~

16

WATER MARCH/APRIL 1997

Pollutant Load Model The m od el has three options for modelling daily pollutant load. The first calculates pollutant load as the product of runoff and pollutant conce ntratio n.

Different pollutant concentrations can be used fo r surface runoff and baseflow.

The dry weather (baseflow) concentration can usually be estimated from periodic water quality sampling. The wet weather (surface runoff) concentration can only be de te rmined from detailed

CATCHMENT

HYDROLOGY

monitoring over several storm events.

In the absence of wet weather data, the CRCCH summary of the range o f event mean concentration (EMC) data from 47 0 Australian and overseas studies can be used as a guide (see M udgway et al 1996; and Figure 2).

However, because of the high variability in the EMC data, the user should realise that 'standard' errors in pollutant loads determined using this data could be 50% to 200% , depending on the water

quality parameter.

The second option uses a power relationship between daily pollutant load and daily runoff LOAD = a RUNOFF 6 There is evidence to suggest that, w he n t here are suffi cient data, the p ower relatio nship leads to better estimates comp ared to the constant p ollutant concentration approach.

However, in determining the empirical paramete rs, a and b, o ne should minimise the errors between the simulated and 'recorded' 100~-- - -- - - - ~- ~ loads in th e linear scale, and ·· n ot in the log scale as is / conventionally done (because 10 ,/ of mathematical simplicitysee Figure 3). This is because / the log scale gives similar /.··. weight w hen minimising the .. e rrors in th e big and small .I Ini~;cept and gradient of the linear es timated loads, w hile in !!, ./regression in this log plol gives practice, it is m u ch more 1i ·· a and b dircclly .2 .01 '---~-~....:...~......~~~important to simulate the I IO 100 "'I:'.: 1 . I bigger loads adequately. ~ ()() Thick line shows power rela1ionship The third option uses a daily with a and b optimised 10 minimise 0 80 the load accounting approach. It SSE between estimaied and ac1ual loads in the linear scale. sim ulates dry weather accumuDotted line is the same lation on impervious surfaces 60 as the top plot. up to a 'catchment characteristic load' and also accounts for 40 pollutant co ntributio n fro m rainfall. This ' process approach' 20 is added only fo r completion, as in practically all cases, there 5 10 15 would not be sufficient data to Daily runoff {mm) j ustify its use.

Figure 3 Daily total suspended solids versus daily

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runoff for a Sydney catchment plotted on linear and log scales (showing that minimising SSE of LOAD, rather than log(LOAD) puts more weight in estimating the large loads accurately)

25

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Recorded runoff Simulated runoff

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Figure 4 Daily runoff and total phosphorus load simulated by the model for a Sydney catchment, 1993

Model Slmulatlons Figure 4 compares the daily ru noff an d total phosp horus (TP) loads simulated by the model fo r a small urban catchme nt in Sydney with the recorded values. It should be noted that the model was not calibrated . Typical parameter values (from authors' experience) were used for the runoff component and two different TP concentratio ns (for surface runoff and baseflow) were used to estimate daily TP from daily runoff.

T he ove rall simulations were relatively good, with the total estimated runoff being 10% less than the reco rded volume and the total TP load being 5% less than the value published in the Sydney W ater stormwater monitoring proj ect report. Nevertheless, the plots in Figure 4 are there only to show the model simulations, and not to illustrate w hat appears to be a relatively good simulation (w hich could have resulted from good fortune).

other Features The main inputs to the C R CCH mod el are fraction imperviousness, pollutant concentrations. daily rainfall, daily PET (or climate), outdoor water use (daily or average annual) and runoff (if calibration is required). T he main outputs are the various components of daily runoff and pollutant loads, and other summaries.

Other features of the model include an algorithm to distribute average annual outdoor water u se to daily values as a function of maximum temperature and rainfall (based on analyses of M elbourne water demand data, see Zhao and McMah on, 1996), an automatic parameter op timisati on rou tine, and recommended parameter values based on the CRCCH research study using data from several Australian capital cities.

The CRCCH daily model is currently being packaged into a userfriendly software and a workshop on the model will be held in mid 1997 .

References Boyd M J, Bufill M C and Knee RM (1993) Pervious and impervious runoff in urban catchments. Hydro/. Sci., 38: 463-478.

Chiew F H S and McMahon T A (1995) Conceptual modelling of daily runoff in urban catchments. Proc. 7th Int. Conf. on U rban Storm D rainage, H annover, Germany, Sept, !AHR/ IAWQ , Seeliger Sofort-Druck, Hannover, Vol. 1, pp. 323328.

Chiew F H S, Osman E H and McMahon T A (1995) Modelling daily and monthly runoff in urban catchments. Proc. 2nd Int. Symp. on Urban Stormwater Management, Melb, July, I.E. Aust., Nat. Conf. Pub!. , 95/3, Vol. 1, pp. 255-260.

Chiew F HS, Stewardson MJ and McMahon T A (1993) Comparison of six rainfall-runoff modelling approaches.]. Hydro/., 147: 1-36.

Mudgway LB, Duncan H P and McMahon T A (1996) Best Practice Environmental Management Guidelines fo r Urban Stormwater.

CR C fo r Catchment Hydrology report fo r Victorian EPA, Melbourne Water and Victorian D epartment o f Natural Resources and Environment.

R obinson M (1993) Changing ideas regarding storm runoff processes in small basins. In: Flow R egimes from International and Experimental Network Data (FRIEND) (Editor: Mark Robinson), Institute of Hydrology, United Kingdom, Vol. 3, pp . 316.

Zhao R J (1992) The Xinanjiang model applied in China.]. Hydro/., 135: 371- 381 .

Zhao S L and McMahon T A (1996) Water D emand Modelli ng fo r Metropolitan Melbourne. Project Research Report, University of Melbourne.

Acknowledgements Data from Sydney, Canberra, B risbane and M elbourne are used for the study. T he data are provided by Sydney Water, AWT -Ensight, ACT Electricity & Water and B risbane C ity Council.

WATER MARCH/ APRI L 1997

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CATCHMENT

HYDROLOGY

Leaf Litter in ¡Stormwater: A Major Source of Nutrients?

R A Alllson, F H S Chlew Int roduction Both deciduous and evergreen trees in urban areas can drop large amounts of litter. i.e. leaves, twigs, bark and needles. T he fallen leaves are potential contributors of nutrients as they break down in catchments and in urban waterways. North American and Australian studies have shown that leaf litter contains 0.05 - 0.45% of total phosphorus (TP) and 0.7 - 1.2 % of total nitrogen (TN) (expressed as a percentage of dry leaf weight).

Experiments also indicate that 5 - 15 % of nutrients in leaf litter can leach into sto rmwater (Cowen and Lee, 1973; Dorney, 1985; Prasad et al, 1990; Attivil and Leeper, 1990; and R iley and Abood, 1995). The ranges of values between different studies illustrate the influence of va rious tree types (evergreen and various deciduous tree species) and catchment conditions.

Estimate of Potentlal Nutrient Contribution The nutrient impact of leaves in stormwater depends on the amount of leaf litter that finds its way into u rban drains. Estimates of leaf litter loads in stormwater were made possible by a gross pollutant (litter and debris) monitoring study in Coburg, an innercity suburb of Melbourne.

As part of the study, a Pollutec CDS trapping device, based on a solid separation mechanism referred to as continuous deflective separation, was installed at the outlet of a 50 ha catchment (65% residential, 30% commercial and 5% light industrial) (Allison et al 1996).

The CDS unit diverts incoming flow and associated pollutants into a screen separation chamber, which is designed to maintain a self-clearing screen. T he t rapped litter settles into a containment chamber. Depth sensors placed on the Table 1 Summary of key results from 10 cleanouts of the Pollutec device (values are totals from the ten cleanouts} Monitoring period

89 days

Catchment area Runoff events Runoff Leaf litter Other litter TP from leaf litter TN from leaf litter

50 ha

13 77 mm 283 kg (dry} 77 kg (d ry} 0.40 kg 4.0 kg

Samples of leaf litter (mainly leaves, twigs and garden clippings) were tested for TP and TN contents. TP In the ten cleans range from 0.08 0.28 % of dry leaf weight. TN range from 0. 7 2.2 %. These are similar to values reported In the literature.

18

WATER MARCH/APRI L 1 99 7

weir which bypasses only the highest flows indicated that less than one percent of flow bypassed the weir during the monitoring period. As such, practically all gross pollutants larger than the screen perforations of the containment chamber (18 by 4.7 mm) were captured by the device.

The containment chamber was cleaned ten times in the autumn/ win ter months between May and August 1996. Table 1 summarises the key results from the monitoring study that are relevant to this paper.

A Major Source of Nutrients?

Monitoring over 89 days indicated that the total TP and TN in leaves that find their way to the stormwater were 0.4 and 4.0 kg respectively. With 77 mm of runoff in the 50 ha catchment over the monitoring period, the T P and TN in leaves in the stormwater can also be expressed as 0.01 mg/L and 0.11 mg/L respectively. Of these, o nly about 5% to 15% can potentially leach into the stormwater (see references in the Introduction) .

Water quality testing of stormwater samples taken in the catchment indicated that the TP concentration of stormwater was generally between 0.3 and 0.6 mg/L (although concentrations as high as 3.0 mg/L were fo und) and the TN concentration was between 1.5 and 4.0 mg/L (concentratio ns as high as 6.0 mg/L were recorded). These concentrations are within the large range ofvalues reported in the literature for fully developed urban areas (see Athayde et al 1983 ; and M udgway et al 1996).

This catchment has a mixture of evergreen and deciduous trees, and it is likely that the gross pollutant characteristics would be different at other times of the year. T he catchment is typical of inner-city suburbs in Melbourne and most parts of Australia.

In any case, the values reported here clearly show that the potential nutrient contribution ofleaflitter in stormwater is about two orders of magnitude smaller than typical nutrie n t loads measured from water samples in urban stormwater.

This implies that removing leaf litter from urban waterways will do little to reduce t he total nutrient load.

H owever, because leaf litter accounts for about three quarters of stormwater gross pollutants (see T able 1; Allison and Chiew, 1995; and refe rences

therein), it must also be considered when designing devices to trap urban stormwater gross pollutan ts . The conclusion also suggests that conventional water sampling bottles (that do not normally admit gross pollutants) provide adequate estimates of total nutrient loads.

References Allison R A and Chiew F H S (1995) Monitoring of stormwater pollution from various land uses in an urban catchment.

Proc. 2nd Int. Symp. on Urban Stormwater Management, Melbourne, July, Inst. Eng. Aust. , Nat. Conf Pub!., 95/3, Vol. 2, 511516.

Allison RA , Wong T H F and McMahon T A (1996) The Pollutec stormwater pollution trap: field trials. Water, 23(6): 29-33.

Athayde D N, Shelley P E, Driscoll E D, Gaboury D and Boyd G (1983) Results of the Nationwide Urban Runoff Program.

USEPA, Washington D .C., PB84- 185537.

Attivil PM and Leeper G W (1990) Forest Soils and Nutrient Cycles. Melbourne University Press, 202 pp.

Cowen W F and Lee G F (1973) Leaves as a source of phosphorus. Env. Sci. & Tech, 7: 853- 854.

Dorney J R (1986) Leachable and total phosphorus in urban street tree leaves. Wat. Air Soil Poll., 28: 439- 443.

Mudgway LB, Duncan HP and McMahon TA (1996) Best Practice Environmental Management Guidelines for Urban Stormwater. CRC for Catchment Hydrology report for Victorian EPA, Melbourne Water and Victorian Department of Natural Resources and Environment.

Prasad D, Henry J G and Kovacko R (1980) Pollution potential of autumn leaves in urban runoff. Proc. Int. Symp. on Urban Storm Runoff, Kentucky, July, pp. 197202.

Riley SJ and Abood M (1995) Impact of water quality of gross pollutants. Proc. 3rd Conf. on Planning fo r Creative Stormwater Management, Syd, September, International Erosion Control Association, pp. 357-370.

CATCHMENT

HYDROLOGY

Pollutant Removal By Storage: Analysis of Australian and Overseas Data HP Duncan The quality of urban stormwater runoff can be improved by temporary storage in lakes, ponds (basins), and wetlands. The main processes involved are settling of suspended material, averaging of dissolved material, chemical reaction in solution, and bacterial action in sediments.

The CRC for Catchment Hydrology has completed a review of existing technical literature on pollutant removal by storage. It will be publishing a range of descriptive guidelines derived from the review, and a statistical analysis of the storage performance data.

Altogether 65 data records were obtained from 51 separate sites in four countries, under a wide range of conditions. The statistical analysis concluded that: • All water quality concentration data analyse d appear to be log- normally distributed.

• Area ratio (basin area/total catchment area) is a better measure of the pollutant removal effectiveness of a basin, than storage (basin volume/total catchment area). In every case where basin size is found to be effective in pollu tant reduction, area ratio is a good measure, and with the exception of one pollutant, it is the best measure.

• For some water quality parameters, input concentration is a highly significant explanatory variable, regardless of w hether output concentration or percent removal is required. H ence input concentration should always be reported in studies of treatm ent efficiency in storage.

• Area ratio and input concentration together can explain up to 89% of the between-study variation in output

Constructed pollution reduction pond in a new Melbourne suburb

quali ty, w hen o utput quali ty is expressed as a concentration, and up to 65% of the variation when o utput quality is expressed as a percentage of input concentration.

• The 11 wate r quality parameters tested fall into three groups, based on their behaviour in storage: - The settling group (suspended solids, total lead, total zinc). Output concentration is roughly proportional to the square root of the input concentration, and inversely proportional to the square root of the area ratio. Under favourable circumstances the removal efficiency can be high.

- The proportional group (dissolved phosphorus, total phosphoru s, organic nitrogen, ammo nia ni trogen, total Kjeldahl ni trogen, total nitrogen, chemical oxygen demand). Output concentration is proportional to input concentration (i.e. percentage change is independent of input concentration), and proportional to area ratio to the power minus 0.1. The overall removal efficiency tends to be poor.

The rate-limited group (oxidised nitroAru Suspended Solids gen). Output concen150 , -- - ==~===--=-==;:;::;-r--,--,---,RaUo 4 34 tration is proportional ss., • ss..''°" Area Rallo'°.lt ' 10 · .002 Std Err" +92~• . -48o/• to input concentration 125 (Mean Blas Fae10r Used • 1.22) to the power 1. 6, and g 100 proportional to area ~ ratio to the power i 75 .02 minus 0.2. At higher ~ input concentrations, u0 50 05 where quality improve1 ment is most needed, ! 25 the removal efficiency 0 is poor.

100 150 200 250 300 350 4(10 0 50 Input Concentration (mg/L) • The derived relationships indicate that two Figure 1 Storage performance curves for suspended smaller basins in series solids removal are more effective at

i

removing pollutants than one larger basin with the same total area ratio, for all water quality parameters tested.

• There is a suggestion (based on a small sample) that combined ponds and wetlands are more effective than either alone, for the same area ratio. This is probably related to the shape effect described in the previous point.

• Wetlands(shallow waterbodies) are significantly less effective than ponds of the same area ratio for removing total copper , all forms of phosphorus, organic nitrogen, and nitrate nitrogen.

No significant difference was found for the remaining quality parameters.

H owever wetlands may be more effective than ponds of the same storage volume, since wetlands tend to be shallower than ponds.

Performance curves were developed for the 11 water quality parameters. As an example, the curves for suspended solids are shown in Figure 1. Although they were calculated using log transforms, they have been adjusted to give the arithmetic mean of the most likely behaviour.

Statistical data is given in the information box on the graph. Note that the error bands are quite wide, even though the relationships are statistically significant at the 95% level.

Authors Professor Tom McMahon is Prefessor ef Environmental Hydrology, and Deputy Director of the CRCCH. Dr. Francis Chlew is Program Leader of the Pollution Load project, Robin Alllson is a R esearch Scholar, and Hugh Duncan is seconded from Melbourne W ater to the CRCCH, all at the University of Melbourne.

WATER MARCH/APRIL 1997

19

CATCHMENT

HYDROLOGY

FLOOD HYDROLOGY Towards Reducing the Uncertainty in Design Flood Estimation P HIii, R G Mein, P E Weinmann Design Flood Estimation More than half a billion dollars is spent annually in Australia on works w hich require an estimate of a design flood. If adequate (>20 years) streamflow data are available, and only an estimate of the flood peak is required, a frequency analysis of recorded flows is recommended.

If streamflow data are not available, a rainfall based estimate is required. For peak flow estimates, simplified methods (eg. probabilistic rational method) may be sufficient. If a design flood hydrograph is required, an event based procedure will be necessary.

D esign hydrograph estimation starts with a design rainfall of the desired annual exceedance probability. As indicated in Figure 1, the probability of the calculated peak will depend upon the choice of the critical storm duration, areal reduction facto r , storm temporal pattern, design losses, runoff model, model parameters and the level of baseflow .

Eac h of these components has a distribu tion of possib le values .

H owever, due to the current lack of information on the true distribution of each of the compone nts (and the complexity involved), some 'central' or 'typical' value of each of the key inputs is taken.

Australlan Ralnfall and Runoff Guidance for design flood estimation in Australia is given in Australian

Design Rainfall Depth •Duration

•Areal reduction factor •Temporal pattern •Losses •Routing model •Model parameters •Baseflow

R ainfall and Runoff (1987 ); [ARR87]. This document is not intended to b e prescriptive or a strict code of practice and , " the use of new or improved procedures is encouraged, especially wh ere these are more appropriate". It goes on to state, "where they (new procedures) are based on observed data or have been shown to reproduce its characteristics, these n ew methods should be used".

Reducing the Uncertainty The unce rtainty in design flood estimation can be reduced by the use of improved procedures or better use of available data. The CRC for Catchment H ydrology' s research program in flood hydrology has made significant advances in several key areas including: Design losses from rainfall. Loss is that proportion of rainfall which does not appear as surfac e runoff N ew design losses parameters have been derived from the empirical analysis of data from 22 catchments in Victoria and the ACT, and are recommended for design flood es timation in southeastern Australia o n the basis that: • they are based on a detailed study using methodology that is consistent with the derivation of design rainfalls; • they incorporate plausible relationships with catchm ent and climatic characteristics, and rainfall duration; they produce satisfactory results w hen tested on 11 representative catchments in the region.

Figure 1 Event Based Design Flood Estimation 20

WATER MARCH/APRIL 1997

Design Flood Peak

Areal Reduction Factors.

Areal

reduction factors (ARF) convert point estimates of rainfall into average estimates over the catchment.

The ARFs recom-

Maroondah Spillway in flood

mended in ARR87 are based on overseas data; recent studies have sh own them to be of only limited relevance to Australian conditions.

N ew ARFs h ave been derived from local data for catchments in Victoria, for rainfall durations from 18 to 120 hours, and for catchment sizes from 1 to 10,000 km2 • These ARFs are considered to be superior to the currently used values and are recommended for adoption in futu re design flood studies for Victorian catchments.

The Future A new CRC projec t " H olistic Approach to Rainfall- based D esign Flood Estimation" will seek to reduce the unce rtainty in design flood estimates by taking account of the interaction and joint probability of the different flood producing components.

It is exp ected t hat su ch a holistic approach will produce the next significant improvement in design flood estimation procedu res.

Conclusion R esearch undertaken in the flood hydrology program of the C R C for Catchment H ydrology has addressed some of the limitations in the design parameters contained in ARR87. T he new design parameters produced results consistent with flood frequency analysis w hen tested on 11 catchments.

This p roject has concentrated on catchments in south-eastern Australia, but the analysis procedures could readily be applied to data from other regions to extend its outcomes.

CATCHMENT

HYDROLOGY

Recent Advances in Estimating Extreme Design Rainfalls P EWeinmann Water Authorities across Australia are currently assessing the spillway adequacy of their dams to determine if costly spillway upgrading works are nccessa1y to comply with current safety criteria. This assessment is aimed at determining the risk of the dam being overtoppcd by a flood that exceeds its spillway capacity. It requires the estimation of a complete design flood frequency curve for the catchment, from "normal" design floods relevant to the design of most hydraulic structures, through rare floods in an intermediate range, to the extreme end of the "Probable Maximum Flood", the design standard for dams whose ovcrtopping would have vc1y serious consequences.

The spillway capacity of most existing dams falls into the range of intermediate floods, where the uncertainty in the current methods of estimation is greatest. This uncertainty is largely associated with the lack of reliable design information on rare to extreme storms. The CRC for Catchment Hydrology's research into the estimation of extreme floods has therefore focussed on providing better estimates of design rainfalls in the range of rare to extreme storms.

The new method developed from this research makes use of the largest rainfall observations from many sites. In the case of Victoria, where the method was first applied, the largest rainfall observations from more than 750

Improvements in Real-time Flood Forecasting J Elliott Advance warning that a river will flood can enable people living and working in the floodplain to take preventative action to reduce the amount of damage caused by the flood and increase their safety and security.

The more accurate the forecast, the greater the potential savings.

To this end researchers at the Cooperative Research Centre for Catchment Hydrology have been examining different methods for forecasting river levels from rainfall data and have identified several methods with potential applicability in Australia.

Particular attention was placed on the way in which observations of river level made during the flood arc used to correct, or update the model, so that subsequent forecasts during an event are improved.

The project looked at a total of seven different models applied to fourteen catchments ranging in area from 234 to 2141 sq km, and compared the performance of the models using a range of statistics and other measures. The results of the project highlighted the importance of using a simple, yet sound, means of accounting for the changes of soil moisture with time using a continuous soil moisture accounting model such as the Australian

Water Balance Model or the Xinanjiang model developed in China and a nonlinear distributed catchment routing model, but also demonstrated the benefits of a simple error correction algorithm to adjust model predictions.

More complex models developed in the UK and USA were included in the comparative study and, while showing an improvement in performance for some catchments, did not outperform the simpler models when considered across all catchments.

The results of the project will be transferred to operational use in Bureau of Meteorology flood forecasting offices during 1997 and have the potential for application in other areas such as forecasting of river inflows for better management of water storages.

Authors Professor Russell Mein is the Director of the CRCCH, based at Monas/, Unit1ersity, J\1elbo11me, r111d is the Program Leader for the Flood Hydrology projects. Dr Peter Hill is Project leader D1, Erwin Weinmann is Project Leader) DJ, both at 1\1011ash University. Jim Elliott is the S11pe1visi11g E11gilleer, Flood Warning, at the Bureau ef Meteorology, 1\1elboume, and is Project Leader) D4.

stations have been used. This allowed confident estimation of24-hour to 72hour design rainfalls for annual exceedance probabilities as low as 1 in 2000. Application of the new methodology to dams in Victoria has confirmed its usefulness in allowing more reliable assessments of the risk factors associated with existing spillways.

Water authorities in other states have shown considerable interest in applying the new methodology for deriving extreme design rainfalls for their regions. The CRC for Catchment Hydrology is actively supporting the transfer of this technology to the other states.

APOLOGIES In the WSAA report in the N ovember/Dccember issue of Water, in the section discussing the NSW EPA Study of the Sydney outfalls, Dr Langford mentioned the polluting effects of stormwater, particularly in Port Jackson. This data was not part of the EPA study, but came from other sources.

*** We regret that the author's biodata for the paper "Recycling of Reclaimed Water in South Australia Qanuary 1996) was omitted. It should have read:

N Mehlika Kayaalp is a Senior Public Health Engineer with the South Australia11 Health Co111111issio11, Adelaide, supervising wastewater facilities i11 areas that are not serviced by the SA Water Corporatio11 sewerage syste111s. She graduated B Sc fro111 A 11kora, and gained Masters degrees fro111 Delft and from Murdoch University, Perth. She hos worked in Turkey, Switzerland, Western Australia and South Australia in both engineering and research.

WATER MARCH/APRIL 1997

21

WATER Abstract We report here the first large scale trial in Australia of a quantitative DST test, known as Colilert-18. The trial consisted of two parts, a straightforward comparison of 406 routine samples by Colilert-18 and MF, and a designed trial constructed to test a range of filtered and unfiltered chlorinated and chloraminated potable waters, in which a total of 164 seeded samples were analysed. A statistical analysis of the overall results clearly demonstrated that Colilert-18 detected more coliforms than MF. There was no significant difference between MF and Colilert18 for detection of E.coli except for filtered chloraminated water, where Colilert-18 appeared more sensitive.

The results are discussed in relation to other trials performed internationally.

estimation of the presence of coliforms and E.coli. The procedure utilises defined substrate technology (DST).

DST is based on a procedure whereby the compounds used for differentiation and/or detection are concomitantly the major carbon and energy sources within the medium. This system is now commercially available and is marketed

Materials and Methods Preparation of "spiked" water samples. 2L of a representative water

type was dosed with a volume of source water designed to give recovery of coliforms and E.coli at the level of 20 80 colonies/100mL. The residual chlorine in the water sample was neutralised using sodium thiosulphate.

Contact time of the inoculum with the test water before neutralisation was 15 s for a free chlorine residual > 0.2 mg/L, and 60 s for a free < 0.2 chlorine residual mg/L. Where chloraminated waters were examined 60 s was found to give recovery of cells within the desired range.

The aim was to give sufficient contact time to stress the bacterial inoculum but allow quantifiable recovery.

TRIALS OF

COLILERT

SYSTEM

Introduction Water utilities throughout the world monitor the microbiological status of potable water by screening for coliform and thermotolerant coliform (essentially E.coli) microorganisms. One method involves inoculation of water directly into a series of tubes containing known volumes of a differential lactose broth.

Following incubation the number of tubes giving a positive result can be analysed statistically to give an estimate of total coliforms, or most probable number (MPN). The second method uses a cellulose acetate filter which is incubated on selective medium at a temperature (MF permissive For thermotolerant technique). coliforms the selective temperature used is 44.5°C, whereas a temperature closer to body temperature (35°C) is used for coliforms. Both MPN and MF techniques yield only presumptive positive data and the inoculation of confirmatory media is expensive, time consuming and adds a further 2-3 days to achieve a final result.

In the truest sense the presence of coliforms but absence of thermotolerant coliforms in a supply is not necessarily indicative of a faecal pollution event. However, the continued presence of such organisms is undesirable as it may indicate ingress or ineffective disinfection of a system.

In 1988 Edberg et al described a new broth culture method for simultaneous 22

WATER MARCH/APRIL 1997

P W Adcock, C P Saint

by IDEXX as Colilert. Colilert contains ortho-nitro phenyl galactopyranoside (ONPG) and methyl umbelliferyl glucuronide (MUG). The first enzyme in the pathway of lactose utilisation is ~-galactosidase. This enzyme can act on ONPG to yield a yellow product, an activity which is indicative of coliform bacteria. E.coli expresses the enzyme -glucuronidase which converts MUG to a blue fluorescent product.

Currently the production of acid and gas following fermentation of lactose is used to definitively identify coliforms.

However, it has been reported that monitoring ~-galactosidase ~ctivity may be preferable, as some co1iforms fail to produce gas following fermentation oflactose (Anon., 1994).

Initially Colilert was only available as a "presence/absence" type test, which for our needs was not wholly adequate, but within the last year a quantitative version has been available in Australia.

Additionally an improved formula allows examination after 18h a.nd the new product is referred to as Colilert-18.

This report details the first major trial of this system on potable waters in Australia. We analysed routine samples and seeded samples of water which had undergone various treatments and disinfection. In all cases equivalent samples ~ere analysed by MF for direct comparison.

Membrane filtration (MF). The procedure was

performed according to that described in Eaton et al (1995) and by Standards Australia, AS4276.1

(1995).

For coliform testing, samples (100mL) were filtered through 0.45µm, 47mm membranes and placed onto pads moistened with lauryl tryptose broth. Plates were incubated at 35°C for 2 h. Membranes were then transferred onto m-endo agar LES and incubated at 35°C for 16 - 20 h.

Typical and atypical colonies were then counted and recorded. Up to 10 colonies were then inoculated into lactose peptone water (LPW) and incubated at 35°C. Tubes were examined for the production of acid and gas at 24 h and 48 h.

For estimation of E. coli, samples (100mL) were filtered through 0.45µm, 47mm membranes and placed on differential faecal coliform medium (DFC) and incubated at 30°C for 4h and then at 44.5°C for 14 h. Typical and atypical colonies were then counted and recorded. Up to a maximum of 10 colonies were then picked and inoculated into E.C. medium and 1% tryptone water and incubated at 44.5°C for 24h. Isolates which gave visible growth and gas production in E.C. medium had the corresponding tryptone water tube tested for the ability to convert tryptophan to indole using Kovacs reagent.

Colllert-18. All reagents, sample bottles and quanti-trays (gamma

WATER Table1 DevelopJ11ent of an In-House Comparator for Colilert-18 Coliform 18h Result

Confirmation 22h

18h

$3,50-Hozon ti,nits'!'. <350 Hazen units

atypical

?50-500 _H_azen Units

typica'I

350-500 Hazen units >750 Hazen-units

* AS defined_ in Eaton et al

:35()-:)00 Hazen units >750 Hazen units

MF -

Total

were indicative of coliforms or

76 13 89

36 281 317

112 294 406

E. coli were confirmed using

_T~li1_e,,:a',rota1'_60JifOm1s: Corri'Par'ison-_of',fyienibr~ne -Filtr,ation with_Colilert-18 at 22_-hoLirS,lncubation 76 13 89

37 280 317

113 293 406

Stfnsltlv!W-=:_ 76/89 _ =-85.4% Speciffc_itY :".' 280/317_--_=,,88.3% Positive_,, Pred_lct_ive Value)= ]6/113-"" -67 ;2% Negative-Predlctlve-,Vatue ,':",-280/293 = 95.6% kappl:'I}' 67.2%

rab'ie-4-'E.,--c_riu: c;-riiP}rJson ,;/ M~inhrane FlltrcitiOn with Colilert:18 at 18h Incubation MF+

MF-

Total

28 5 33

9

361 370

37 366 403

SensitiVity,,; 28/33 = a4;a% Specificity= 361/370 ':"'97.6% PosiUve,Predlctive Value= 28/37 = 75.7% Negative Predictive Value= 361/366 = 98.6% kappa'= 78.1%

Table: 5 Differences-Between Coliform and E.coli Numbers Detected by Membrane ,Filtration and Colilert-18 Totarcoltforms t-stat!stic* P-value measured-by: 1 MF Vs Coljlert-18 at1.8:!10urs

-6.9 Oh 405df

P<0.001

2 MF vs .Colilert'18 at 22 hours

-7 .8 on 405df

P<0.001

3 Colilert-18 at 18 hOu'rs vs 22 hour.S

-5.4 on 405df

P<0.001

-1.0 on 402df

P=0.16

E coll measured by: 4 MF VS Colilert-18

Confirmation of Colilert Cultures. Those wells which

MF+

Sensitivity_= 76/89 ':" 85.4% Specificity:= 281/31T=-_88,6% Posjtive Predlct[ve_Value ':"'76/i12 = 67.9% Negative,Predlct!ve Vallie__ = :281/294 =-95.6% k_appa =,67.7%

Colilert-18 + Colilert'18 Total

positive

then transferred to a 35°C incubator for up to 22 h.

After 18 h incubation, yellow and fluorescent wells were counted and recorded. Trays were then incubated for a further 4h at 35°C. Following this period yellow wells were counted as containing presumptive coliforms and fluorescent wells as containing presumptive E. coli. Fluorescence was measured using a commercial U.V. illuminator at 366nm. Each quantitray contains 51 wells and most probable number tables were consulted to give a final count per 100 ml.

Filtration with Colilert-18 at 18 hours Incubation

Colllert-18 + Coli!ert,18 • Total

negative

(1995).

_Table_2_Totai Coliforms: Comparison ofMen,brane

+

negative positive

j)ositiwi

sterilised) were supplied by the manufacturer (IDEXX Laboratories Pry Ltd., Sydney). Samples (100ml) were added to sterile bottles. Colilert-18 snap-packs of powdered reagent were opened and immediately added to samples, which were mixed by shaking.

The powder took about 2 min to dissolve after which the sample was placed aseptically into a quanti-tray and placed into a commercial heat scaler (IDEXX). Sealed trays were placed into a water bath for 20 min at 35°C and

Colilert-;18 Colilert-18Total

22h Result

,,::350 Hazen units 500->750 Hazen units

'I: Analjsls based oh tog8rithms of original observations

the following procedure. The backs of the quanti-trays were wiped over with 709'6 ethanol then wells were pierced with sterile toothpicks which ,vere used to inoculate m-endo agar LES and MacConkey agar, and plates were incubated at 35°C for 24h. Initially all wells were subcultured to estimate the rate of false negatives. Of765 wells tested no presumptive negative wells were found to contain coliforms. Subsequently only fluorescent wells and wells which showed various intensities of o-nitrophenol production were tested. Further analysis of colonies arising depended on whether the original well was indicative of coliforms or E.coli. Lactose fermenting colonies -which originated from coliform wells were subcultured onto blood agar and into LPW and incubated at 35°C. Blood agar plates were examined after 24h and individual colonies checked for cytochrome oxidase activity.

LPW was examined after 24 and 48h for lactose fermentation (acid and gas production).

Isolates indicative of E.coli were subcultured to blood agar, E.C. medium and tryptonc broth and incubated at 44.5°C for 24h.

E.C. medium was checked for visible growth and gas production. The corre-

spending tryptone water was tested for indole production using Kovacs reagent.

Isolates which were cytochrome oxidase negative, and grew in the presence of bile salts and fermented lactose to produce acid and gas at 35°C were reported as confirmed coliforms.

Isolates which were cytochrome oxidase negative, grew in the presence of bile salts, fermented lactose to produce turbidity and gas, and produced indole from tryptophan at 44.5°C were reported as confirmed E. coli. Isolates that were cytochrome oxidase negative and did not confirm by standard procedures were identified using Microbact 24E or BioMerieux Vitek Gramnegative identification cards.

Results and Discussion Overview. The trial consisted of two main parts. The first part was simply a straightforward comparison of Colilert18 versus MF using standard routinely processed samples received at the laboratory. There was sample bias in the sense that in excess of 90%> of our routine samples are negative for coliforms and faecal coliforms, therefore to assure a statistically valid comparison, samples were chosen where low chlorine residuals had been recorded and also where previous samples from the same location had given positive results. The initial statistical analysis was based on presence / absence to reveal if Colilcrt-18 showed comparable sensitivity and specificity to MF. During some preliminary experiments we noticed that some wells showed vaiying intensities of colouration at 18h. Using the standard Colilcrt comparator these wells would have been scored negative at 18h but positive at 22h. These wells were considered to be atypical. After 18h confirmation rate for typical Colilert-18 isolates was 99.5%, however for atypical isolates the rate fell to 66%. This led to a comparator being developed for examination at 18 and 22h. Table 1 details the criteria which when adhered to resulted in a conformation rate of 99.8%. This made it necessary to ascertain whether there was any significant difference in numbers of coliforms recorded between MF and Colilert-18 incubated for 18 or 22h, and also compare Colilert-18 at 18h to Colilert-18 at 22h. A total of 406 samples were processed.

The second part of the trial concentrated on assessing the four major treated water types encountered in South Australian systems, namely: filtered chlorinated, unfiltered chlorinated, filtered chloraminated and unfiltered chloraminated. This experiment was designed to satisfy testing authority standards for the evaluation of a new WATER MARCH/APRIL 1997

23

WAT I: R technique prior to its registration as a standard procedure. The US EPA guidelines for such assessment were adhered to in that at least 10 samples from the four water types were analysed in quadruplicate by MF and Colilert-18 (Bordner et al 1978). Colilert was examined at 18 and 22h.

Analysis of Routine Samples Sensitivity, specificity and predic-

tive value. A previous statistical analysis comparing MPN to Colilert (Finlay et al 1995) was utilised in this study.

Specificity, sensitivity and predictive value were calculated for MF and Colilert-18, taking the former as definitive of whether coliforms were present.

Cohen's kappa was used to identify the level of agreement between the two methods. In all cases significantly high levels of kappa were seen. Tables 2 to 4 present the relevant data for Colilcrt-18 incubated to 18h, 22h for coliform detection and 18h for E.coli. In all cases high sensitivity and specificity were observed, with strong predictive value.

Quantitative analysis. The next step was to ascertain whether the data indicated a significant difference in detection of coliforms and E. coli benveen the t\Vo methods. The original counts in the first trial were transformed into logarithmic data. To compensate for zero counts one was added to all data before the logarithm was estimated using the equation: log 10 (y+1).

Paired t-tests were carried out on the log-transformed data. The log of the total number of colifonns detected by MF was compared to the log of the total number of coliforms detected by Colilert-18 at 18 and 22h. Colilert-18 at 18 and 22h were also compared. An identical analysis was performed comparing E. coli detection with MF to Colilert-18 after 18h. The results of the analysis arc presented in Table 5.

For t-statistic analysis a figure less than -2 is considered significant and for P-value <0.05. Therefore Colilert-18 at both 18 and 22h detected more total coliforms than MF. There was also a significant difference in the number of coliforms detected by Colilert-18 at the t\Vo times. There was no significant difference bet\Veen the number of E.coli detected by MF and Colilert-18.

This is an extremely important finding in relation to monitoring of potable water quality. It was decided to apply another more conservative statistical analysis to this data as a surety. A Wilcoxon signed rank test was applied.

This involved converting the original coliform count for each sample to a proportion of the maximum detection limit allowed by the test. For MF this figure was 100 and for Colilert-18 it was 200. The ranks of these proportions were then compared. Results were in 24

WATER MARCH/APRIL 1997

complete agreement with those in Table 5.

Analysis of Seeded Waters The main treated water types encountered 111 South Australia were tested according to the sampling regime recommended by Bordner et al (1978) for comparative testing of microbiological methods. A total of 164 samples were analysed. After a comparison of all four water types separate analyses were carried out.

Comparisons appear in Table 6.

Overall results demonstrated that Colilert-18 consistently detected more coliforms than MF and that there was a significant difference between an 18 or 22 h incubation. However, with E.coli MF was generally as sensitive as Colilert-18. The one water type which did not agree with this scenano was 'filtered chloraminated'. Here there was no advantage 111 coliform detection by CoJilert18 but a significant one for the detection of E.coli. Again there was a significant difference between incubation of Colilert-18 for 18 or 22h.

For the waters we tested our data clearly demonstrates the need for a prolonged incubation of Colilert-18 up to 22h.

Initial examination at 18h is appropriate as clearly yellow or fluorescing wells can be reported as a confirmed count.

However, a further examination should be done at 22h to give a final confirmed count so that remedial action can be taken at an earlier stage.

Table 6 Differehces ii, -Recoveiy Of C6!iforrn's-andE coli:by_ Me'.rnb_rane Filtration and __Coliler:t¡18 from four types of Seeded Waters t-statlstlc

P~value

-3.7 on40df -5.3 .on 40df -7,8 on 40df

0.02 0.000 0.000

-0.6 on 40df -1.5 on 40df -3.8 on 40df

0.292 0.154 0.000

-2.7 on 9df -3.1 on.9df -3.5 on 9df

0.011 0.006 0.006

0.3 on 9df -0.7 on 9df -3.6 on 9df

0.511 0.260 0.006

1.0 on 9df -0.9 on 9df -4.7 on 9df

0.829 0.208 0.001

-2.8 on 9df -3.4 on 9df -1.9 on 9df

0.010 0.004 0.087

-1.7 on 9df -3.3 on 9df -7.6 on 9df

0.067 0.005 0.000

0.8 on 9df 0.5 on 9df -1.3 on 9df

0.782 0.698 0.219

-3.2 on 10df -4.1 on 10df -5.3 on 10df

0.005 0.001 0.000

0.3 on 10df -0.2 on 10df -2.1 on 10df

0.597 0.439 0.062

OYE!J~l,I ,, _Coliforms MF vs Colilert'f8 at18h MF vs Colilert,18 at 22h Colilert-18 at 18h vs 22h ÂŁ.'coli MF vs Colilert-18 at 18h MF vs Colilert-18 at 22h Colilert-18 at18h vs 22h Filtered Chlorinated Co/iforms MF vs Colilert-18 at 18h MF vs Colilert-18 at 22h Colilert-18 at 18h vs 22h E.co/1 MF vs Colilert-18 .at i8h MF vs Colilert-18 at 22h Colilert-18 at 18h vs 22h

FIitered Chloraminated Coliforms MF vs Colilert-18 at 18h MF vs Colilert-18 at 22h Coli!ert 18 at 18h vs 22h E.coli MF vs Co!ilert-18 at 18h MF vs Colilert-18 at 22h Colilert-18 at 18h vs 22h 0

Unfiltered Chlorlnated Co/iforms MF vs Colilert-18 at 18h MF vs Colilert-18 at 22h Colilert-18 at 18h vs 22h E.coli MF vs Colilert-18 at 18h MF vs Colilert-18 at 22h Colilert-18 at 18h vs 22h Unfiltered Chloramlnated Co/iforms MF vs Colilert-18 at 18h MF vs Colilert-18 at 22h Colilert-18 at 1811 vs 22h E.coli MF VS Colilert¡18 at 18h MF VS Colilert-18 at 22h Colilert-18 at 18h vs 22h

How Does Our Data Compare?

There have been several trials of Colilcrt which have compared the product to both multiple tube dilution and MF. It should be noted that few trials have been quantitative in nature, as it is only recently that the quantitray technique has become available.

However, it is possible to perform a statistical analysis on a presence/ absence basis. Studies which found no significant difference between standard methods and Colilert for coliforms and E.coli include a series of studies by Edberg et al (1988, 1989, 1990 and 1991) in the USA, Argent et al (1991) and Cowburn et al (1994) in the UK, Clark and El-Shaarawi (1993) in Canada and Finlay et al (1995) in New Zealand. The series of studies in the USA were quantitative in that Colilert was set up as a tube MPN procedure.

Distribution water, source water, surface and sub-surface waters and treated effiuents were all evaluated in these studies. Other studies have found Colilert to be acceptable for the testing of total coliforms only (Lewis & Mak, 1989; Gale & Broberg, 1993).

However both these studies recorded relatively low numbers of samples containing E.coli, making valid statistical comparison difficult.

The results presented here strongly support the conclusion that Colilert-18 is an acceptable alternative to the standard MF procedure for assessing the bacteriological quality of potable water.

Indeed Colilert-18 may well result in a better standard of detection, as this study clearly demonstrates its superiority in the detection of coliforms in drinking water, and one recent study has shown its ability to detect potential pathogens which might normally go

WATER undetected (Berger, 1994). The potential benefits of adopting this system fo r the testing laboratory and the client are great. The re is a considerable reduction in staff time devoted to the processing of samples and the rapidity of results and increased accuracy (especially relating to coliform analysis) sho uld ensure increased customer satisfaction.

Acknowledgements T he authors thank the technical staff of the Microbiology Unit, A WQC, for their valuable assistance in this trial. M r R eg Walters, Senior Microbiologist, AWQC, is acknowledged for useful comments concerning the manuscript, and Assoc. Prof. D on Bursill, Group M anager , AWQC, for autho rising financial support for the project. We are grateful to Ms Ly nne Giles at The Flinders University o f South Australia, who performed the more co mp lex statistical analyses . Thanks are also extended to Mr Rich Obrey, Food and Environme ntal Division, IDEXX laboratories Pty Ltd, Sydney, for the provision of Colile rt-1 8 consumab les.

References Anon. (1994) "The Microbiology of Water 1994, Partl - Drinking Water," R eport on Public H ealth and Medical Subjects No. 71 , HMSO, London.

Argent V A, Booth N E, Flynn T, Jones C E, KentJ ,Man BN, andReed RH (1991) A

pilot UK evaluation of a rapid Defined Substrate method for enumeration of total Coliforms and Esc/1eichia coli in water.]. Inst.

Wat. E1wiro11. Ma11ag., 5, 413-41 8.

Bordner R, Winter J and Scarpino P (1978) 'Microbiological methods for monitoting the environment: water and wastes,' EPA600/ 8-78-017, U. S. Environmental Protection Agency, Cincinatti, Ohio, USA. Berger S A (1994) Increased protection afforded by the D efined Substrate T echnology Colilert system by its ability to detect Shigella ~-glucuronidase. Letts. Appl. Microbial. , 19, 53-56.

Clark J A and EI-Shaarawi A H (1993) Evaluation of commercial presence/absence test kits for detection of total Coliforms, Escherichia coli, and ocher indicator bacteria.

Appl. E11viro11. Microbial., 59, 380-388.

CowburnJ K, Goodall T, Fricker EJ, Walter K S and Fricker C R (1994) A Preliminary study of the use of Colilert for water quality monitoring. Letts. Appl. Microbial., 19, 5052.

Eaton A D, Clescern L S and Greenberg A E (1995) 'Standard Methods for the E xamination of Water and Wastewater,' American Public Health Assoc., Washington DC. Edberg S C, Allen M J and Smith D B and The National Collaborative Study (1988) National field evaluation of a Defined Substrate Method fo r the simultaneous e numeration of total Coliforms and Escherichia coli from drinking-water: Comparison with the standard multiple tube dilution method,'' Appl. E11viro11. Microbial., 54 , 1595-1601.

Edberg S C, Allen M J and Smith D B and The National Collaborative Study (1989) N ational fi eld evaluation of a Defined Substrate Method for the simultaneous enumeration of total Coliforms and

Escherichia coli from drinking- water: Comparison with presence/ absence techniques," Appl. Environ. Microbial., 55, 1003-1008.

Edberg SC, Allen MJ , Smith DB and Kriz NJ (1990) Enumeration of total Coliforms and Escherichia coli from source water by the Defined Substrate T echnology. Appl.

E11viro11. Microbiol., 56, 366-369.

Finlay R K, Millar J A and Whyte R J (1995) 'Detection of total Coliforms and Escherichia coli in drinking-waters: Comparison of a standard multiple wbe fe rmentation method with Colilert and Colisurc,' Report FW95/20, lnstiwte of Environmental Science and Research Ltd., Christchurch , NZ. Gale P and Broberg P J (1993) Evaluation of a rapid, Defin ed Substrate Technology method for enumeration of total Coliforms and Escherichia coli in chlorinated drinkingwater. Letts. Appl. Microbial., 17, 200- 203.

Lewis C M and Mak J L (1989) Comparison of membrane filtration and autoanalysis Colilert presence/ absence techniques for analysis of total Coli forms and Escherichia coli in drinking water samples. Appl. E11viro11.

Microbial., 55 , 3091-3094.

Authors Both authors work at the Australian Centre fo r Water Quality, Bolivar, South Australia 5108. Philip Adcock is a Senior Technical Officer, and has worked fo r 18 years in diagnostic microbiology.

Dr Christopher Saint gained his PhD from the University of Wales in 1986. He has 15 years' experience in applied microbiology, both academic and research.

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25

WATER on the bacterial indicator enterococci).

According to the report, the worst dry weather sites were Little Sirius Point and Little Sirius Cove, both The new Taronga Zoo Wastewater adjacent to Taronga Zoo. Ian Kiernan Treatment and Reuse Plant has been had been aware of this problem and in hailed as a world-class example of 1993 gathered a group together to look Australian ingenuity and technology. at how to find a solution. The Commissioned in mid-November 1996 Wastewater Treatment and Reuse Plant

by NSW Environment Minister, Pam concept was born and took three years Allan, the plant will effectively remove a to complete. point source of pollution from Sydney Harbour, recycling 60% of the 400 Facts and Figures The new Taronga Zoo Wastewater kilolitres of water used daily at the zoo.

Treatment and Reuse Plant: A world first for a zoo, the new plant cost more than $2.2m to develop and • took three years to complete from construct. It was also the first Clean Up concept to commission Australia 2001 project to be completed. • 2.5 km of pipeline was laid in the zoo (A Westpac community project, Clean grounds Up Australia 2001 aims to identify and • the plant treats enough water daily to restore 2001 environmental problems supply an average household for a year • is the first plant of its type in any zoo by the year 2001.)

The treatment plant was initiated by in the world Clean Up Australia's chairman and • is located above Sirius Cove Mosman founder, Ian Kiernan, as a joint venture NSW with Taronga Zoo. Together, they • uses Australian technology coordinated a team of government and • has a design which is appropriate for industry leaders to create a world first other harbour side businesses. for environmental conservation (see list New Plans of sponsors at end).

There are now new plans in the The Taronga Zoo plant incorporates state-of-the-art Australian environmen- pipeline for the zoo. These include a tal technology. It will treat, disinfect plan to instal a hie-digester to convert and recycle the zoo's wastewater-using the solid animal waste and putrescent biological treatment, microfiltration waste from the zoo's food outlets into and ultraviolet disinfection technology high-grade organic fertiliser as well as to treat up to 250 kilolitres of water generating electricity at the same time.

Following the completion of the daily. The water will then be reused for hosing down animal enclosures, filling Taronga Zoo project, Clean Up exhibit moats, for flushing toilets as well Australia, in conjunction with Westpac and Sydney Water, is poised to embark as for watering gardens. , 'Not only will it help improve the on another series of projects including a state of the environment but the plant plan to use water from Busby's Bore will save the zoo approximately $50,000 (the original water source for Sydney's a year in water charges and is show- early settlers) in conjunction with other casing innovative Australian technol- sources to water the Royal Botanic ogy, paving the way for valuable export Gardens and the Domain. dollars,' Ian Kiernan said, speaking at Sponsors the commissioning.

Already the Taronga Zoo plant has Sponsors of the plant are: Sydney attracted international attention, with Water Corporation, ANI-Kruger, the delegations from south Korea, China NSW Department of Public Works and and Japan having toured the plant. The Services, the NSW Government, James plant has also broken important new Hardie Pipelines, Environment environmental grounds as a result of its Protection Authority, Civil and Civic, development. Through its involvement Memtec, Walker Civil Engineering, in the project, the Environment Wreckair, Siemens, Multiplex, Hymix Protection Authority (EPA) has been Concrete, Coates Hire, Ke1air Pumps able to implement and refine the limits Australia, BHP, CSR Readymix, recommended in the Guidelines for Urban Grundfos Pumps, John R Keith, Roda and Residential Use of Reclaimed Water.

Pipeline Products, Tradelink.

The sponsors provided support, Background planning, design, advice, pipelines, The Harbourwatch 1995 Season filtration systems, plant, concrete and Report revealed that most sites in electronic systems. Taronga Zoo Sydney Harbour had acceptable water Botanic Estate staff landscaped the site quality less than 90% of the time (based using Australian native plants.

World First for Taronga Zoo Plant

26

WATER MARCH/APRIL 1997

Biological Nutrient Removal Fifteen people attended the seminar at Sydney's Wynyard Vista Hotel on 2 December, 1996 to hear a very interesting talk on trends and developments from one of the pioneers of this field.

Dr James Barnard, Reid Crowther (Canada) who are affiliated with CMPS&F in Australia, started by giving an overview of the scenario in North America, where discharge limits for nutrients are tightening (eg, Oregon where P must be 0.08 mg/L, and Northern Florida, Total N 3 mg/L). In Western Canada, nutrient removal is based on biological removal of P, whereas in Eastern Canada, chemical control is advocated.

There has been a proliferation of various processes to control P, including A/O, A2/O. VIP, VIPR, UCT. Dr Barnard has now developed the SAP Process (State of the Art Process) which involves pre-anoxic, anaerobic, anoxic and aerobic zones with a 10 % recycle to the pre-anoxic. Dr Barnard stated that the intermittent system doesn't remove N and P to the same levels as continuous systems because there is no optimisation of the use of the available carbon source.

Dr Barnard spoke about the role of VFAs in P uptake in biological systems.

Fermenters were typically required for colder climates, since the sewage will not be fermented. Alternatively addition of acetic acid was an option.

Kelowna and Westbrook plants (Canada) have been very successful in achieving high P removal. Calgary is the latest BNR plant. Plants may now be designed to remove P biologically to as low as 0.25 mg/L. Typically Bio P plants will take some 7 days to develop removal capability.

Dr Barnard spoke about two types of bulking. One can be cured with application of selectors. The other relates to the formation of NO compounds.

There is a need to design for the occurrence of simultaneous nitrification / denitrification in the system. An average SS in clarified effiuent is achievable.

Freemantle Prison Tunnels Remediation Bob Mcgowan of Dames and Moore told a fascinating story to a combined meeting of the International Association of Hydrogeologists and the WA Branch of the AWWA on October 7th, 1996.

WATER Under the Western Australian port city of Fremantle lies a series of tunnels that are more than 100 years old. These water galle ries excavated along t he watertable in the limestone were built as part of the Fremantle w ater supply infrastructure. The 1 km of tunnels were constructed in the 1890s over a period of five years using convict labo ur. The tunnels are up to 18m below the ground and in places lie below the watertable.

In the late 1980s, a prison groundskeeper at t he now closed Fremantle Prison noticed irrigation water used to water the prison roses contained diesel oil. H e promptly alerted the appropriate authorities.

It was found that 85 000 litres of diesel had infiltrated the tunnels. The then Enviro nmental Protection Authority pumped out 65 000 litres of the oil, but the clean-up was halted because oil continued to seep into the tunnels at a rate of2 000 litres per week.

Dames and Moore were called to conduct an investigation and organise a remediation program for the area.

The first task was to identify the source of the diesel. This was difficult: a number oflocal organisations including the Navy, BP , Fremantle Prison and Caltex had diesel delivered to them via a complex array of underground pipes.

The source was eventually identified as being a leak in the Caltex diesel supply line ru nning from Kwinana, approximately 15 km south of Fremantle. The offending section of pipe was leased from the Navy and was originally constructed as a mild steel water main in the 1940s.

The leak was at the Fremantle end of the pipe very close to the water supply tunnels. The pipe has since been closed.

The contamination was limited to the tunnels and the area of soil directly around the pipe leak.

Bioremediation of the affected area posed a series of difficult and unique health and safety issues. The oxygen levels in the tunnels were only 14.3 vol %, well below the minimum safe levels of 19 vol %. The atmosphere was dense with hydrocarbon vapours and hydrogen sulp hide and the tunnels were flooded. T he water in the tunnels had an average of 15 - 20 mm of diesel on its surface and in places up to 75 mm.

Those involved in the clean- up were required to access the tunnel via a 17 m vertical shaft. This was made even more difficult by the closed circuit breathing apparatus workers were required to wear in the initial stages of the operation. After having plunged to a depth of 17 m into flooded tunnels of total darkness, w here the sand-absorbing effect of the tunnels made communication with fellow worke rs nigh on

impossible, workers had to board small boats with all their equipment. Boats were considered to be the only safe and p ractical method of manoeuvring around the tu nnels.

O ther risks faced by the team were heat stress caused by the high temperatures and humidity in the tunnels. Very old artesian boreheads in the vicinity meant there was also a very real risk of the tunnels completely flooding.

Dames and Moore considered in-situ remediation but this was deemed as being too slow. Supplying oxygen to enhance biological activity was considered in the bio-ventilation option. They looked at stimulated in- situ bioremediation adding both nutrients and oxygen. They thought of pumping out and separating the contaminants but decided that this would not have dealt with the contamination of the tu nnel walls. Vapour extraction was considered but also deemed too slow. Containment of the contaminants by sealing the tunnels was also considered. In the end it was decided to go for the stimulated in-situ bio-remediation option.

The bioremediation process began in 1992. In the first stage, mine ventilation equipment consisting of fans and flexible distribu tion duct work was used.

About half the tunnels were ventilated and the resulting air flow was used to ventilate the remainder. A continual

oxygen supply was critical, as without it bacterial and fungi die- off would be rapid. Power failure experienced in the Fremantle area during this period served to complicate the process.

Nutrients were supplied at a ratio of 1 part phosphorus : 10 parts nitrogen : 100 parts diesel. Dosing of nutrients was only performed at the northern end of the tunnels. T he southerly movement of water in the tunnels ensured distribution of the nu trients throughout the rest of the tunnels.

D espite the difficult working conditions, most of the free diesel and m uch of the tunnel staining was remediated by 1995. It looks like Western Australia is to have a new tourist attraction. The tunnels are proposed to be opened to the public in the near future.

Serving Small Communities The first speaker at the Victorian Branch's meeting on 'Serving Small Communities' was Warren Wealands , from the Water Bureau at the Department of Natural Resources and Environment. H e outlined the State Government's current policy of achieving W H O health-related drinking water quality in all water supplies by 1999 and

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27

WATER meeting EPA effiu ent licence conditions by 200 1.

The Bureau recently commissioned two studies. The first was a guideline to help authorities to plan and implement low - cost sewerage schemes. Warren presented matrix-type evaluations.

The second document, a report on low-cost water quality improvement options, provides background information on a range of options from management techniques to full treatment and details costs and effectiveness.

Warren said the State Government had committed $20.7m in grants over the next three years to help authorities meet state policy objectives.

28

WATER MARCH/APRIL 1 997

Lachie Campbell, th e CEO of Grampians Water, outlined the special challenges involved in serving small Grampia ns Wate r co mmunltles. provides services to an area of 60 000 sq. km (the size of Tasmania) with a population of sixty thousand. Many towns have a static or falling population.

Some are characterised by a predominantly ageing community, many o f whom relied on social sec urity pensions.

Seventy per cent of the towns were supplied with water from WimmeraMallee Water via lengthy irrigation cha nnels. The wholesale price to Gram pians Water varies from 18c to 54c/kL. This made it difficult to provide

economic service improvements.

Although the level-of-service to be provided was ultimately the decision of its customers, Grampians Wate r has developed a preliminary strategy with the following approximate distribution of water quality service levels: • o ne t hird to WHO qu ality (Ararat-Stawell- Horsham corridor) • one third to intermediate quality • one third to be declared non-potable.

Rick Jackel and Jenny Stewart of Caliban Water presented d etails of recent imple me ntation methods for upgraded water quality and sewerage se rvi ces at some of Caliban's small communities.

Rick discussed the recent Malmsbury sewerage scheme, carried out by a design and construct (D&C) method, following community consultation and value management sessions.

Some innovations introduced in this scheme: • flatter than normal sewer grades • n o manholes were constructed.

It was estimated that savings of 25% were achieved ove r traditional schemes.

J e nny spoke about the ' Nine Western Towns' project. This involved packaging the water treatment requirements for nine small towns into one D&C contract. This compares w ith the traditional approach that may have involved up to 18 contracts for the same work.

The successful contractor (contract value $6.Sm), chose to install four water treatment plants with pipeline connections being made to service all nine Caliban's project commu111t1es. management has bee n based on a ' hands- off, QA- orie n tated approach with no clerk- of-works.

Rick co ncluded by outlining t he potential role and benefits of the D&C model. He believed that a project size of $50 ,000 to $Sm could be appropriate for this method of delivery. The advantages of packaging a number of projects into one can include: • attractive contract sizes • faster implementation • less project management time.

H e advocated a managemen t approach that focussed on service delivery and outputs. By using this approach, o nly four Caliban e ngineers were involved in successfully managing $20m worth of diverse capital projects.

ENVIRONMENT

Summary A fi ve year, mu lti-disciplinary Environmental M onitoring Progra m (EMP) has measured the environmental perfo rmance of Sydney's new deepwater outfalls against a wide range of criteria rel.iced to impacts on marine ecosystems and on human utilisati on of marine resources . It also provided a baseline description o f elements of the Sydaey Deepwater Olllfalls

lrnvlroaBlftlal Moaltorl., ......,._ Titles In the Flnal Report Serles.

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\lot 1. Assessment of the Deepwater Outfalls Vol 2 Sewage Plume Behaviour Vol 3 Water Quality Vo ii Trace Metals and O~nochlortncs In the Marine Environment Vol 5 Impacts on t'1e Marine Ecosystem Vol 6 Database Vol 7 Bibliography Available from NSW EPA, PO Box 1135, Chatswood 2057

ecosystems fou nd off Sydney and has developed an insight into some of the processes w hich determine the exten t to w hich these ecosystems are expo sed to, and affected by, effluent from the deepwater ou tfalls.

Generally, the EMP found that the deepwater outfalls are pe rfo rming well: th ey h ave mitigated most o f t he e nvironmental problems previously experi enced w he n shoreline ou tfalls were operating without creating any maj or new problems in th e ocean waters in the sho rt term. Desp ite the gene rally good pe rfo rmance of the outfalls, there are a number of residual environmental issues associated wi th the operation of the outfalls including: â&#x20AC;˘ poten tial for acc umula tions of sewage particles and associated contaminants in offshore sediments; and â&#x20AC;˘ unexplained minor changes in abundances of certain bottom dwelling organisms and free swimming fish near outfalls.

Detailed results o f EMP studies, an

assessment of the p erformance of the deepwater o utfalls and a summary of othe r mo nitoring are provided in the EMP Final R eport Series published by the New South Wales Environment Protection Au thority (EPA) .

Introduction Abou t 80 per cent of Sydney's total sewage flow is discharged to the ocean after p rimary treatment at Malabar, North H ead and Bondi sewage treatment p lants (STPs). Over the last decade or more t he community has voiced growing concern s about the effects of discharges of sewage to the ocean. One measure to address these concerns has been the construction of deepwater outfalls.

Before t he comm1ss10nmg of deepwater outfalls, discharges at cliff face outfalls often led to poor beach and bathing water quality (Robinson et al., 1996), high levels of some contaminants in certain fish (Lincoln- Smith and WATER MARCH/APRIL 1997

29

ENVIRONMENT Mann 1989a & b; McLean et al 1991) and reduced diversity of some biological communities at least in the immediate vicinity of the outfalls (Fairweather, 1990). The gross visual impact of eilluent from the forme r cliff face outfall at North Head is clearly evident in Figure 1.

The locations of the Sydney deepwater outfalls and the sewerage catchments which they serve are shown in Figure 2.

The first deepwater outfall was commissioned at Malabar in September 1990.

This was followed by the commissioning of deepwater outfalls at North H ead in December 1990, and at Bondi in August 1991. The outfalls are described in Table 1. Figure 2 also shows the reduction in the frequency of visible sewage pollution o n beached following the commissioning of the outfalls, as discussed below This paper presents a summary of the results from the EPA's Sydney Deepwater Outfalls Environmental Monitoring Program (EMP), the multidisciplinary study that measured the performance of the outfalls.

The EMP developed a predictive understanding of t he be haviour of sewage plumes so it was possible to assess the extent to which monitoring

sites were exposed to the sewage eilluent during the EMP. The fate of a range of known eilluent constituents were investigated directly through monitoring in the water column (faecal bacteria, n utrients and suspended solids), in deployed oysters and in fish (contaminants), in sedim ents (contaminants and sediment characteristics) and o n beaches (faecal bacteria and sewage grease).

Further studies measured the impacts of efiluent on marine ecosystems (fish and benthos) and on human u tilisation of marine resources (seafood contamination and recreation). These studies generally looked for changes which could be attributed to the commissioning of the deepwater outfalls by comparing changes observed at outfall sites with those at distant control (reference) sites using methodologies based, to va1ying degrees, on those espoused by Green (1979) and U nderwood (1991, 1992, 1993).

The EMP was conducted mainly by the EPA and its consultants during the period from 1989 to September 1993 mostly in the area from Broken Bay to the Royal National Park and up to 15 kilometres offshore. T his assessment of the pe rformance of th e deepwater I

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Figure 2 Map of the EM P's Sydney study area showing the deepwater outfall locations, sewage treatment plants and t heir catchments. Visible sewage pollution is also shown before and after commissioning of deepwater outfalls (based on EPA Beachwatch data from November 1989 to May 1993) 30

WATER MARCH/APRIL 1 99 7

Nature of the Effluent T he sewage received at the North Head, Bondi and Malabar sewage treatment plants (STPs) consists of waste waters from residential, industrial and commercial pre mises, as well as substantial amounts at times of rainwater and groundwater.

T he most extensive information available on the nature of the eilluent is provided in licence compliance reports prepared by Sydney Water (or the then Water Board). Some of this information has been analysed by Pritchard et al (1996a). Comparisons be tween the three ST Ps were based on compliance data fro m 1994/95 when contaminant analyses were standa rdised across all STP s.

The concentrations of most of the measured contaminants were broadly similar at all three sewage treatment plants, at least in recent times. The composition of eilluent from Malabar STP is shown in Table 2. Of the three plants, Malabar discharged the greatest volume of waste water and p robably contributed the highest load of each contaminant.

The compliance monitoring data suggest that suspended solids and grease loads decreased by about 30 to 50 % during the course of the EMP (Figure 3). These reductions have been attributed to a combination of factors including improved treatment efficiencies, cessation of the discharge of digested sludge to the ocean and better source control, especially through trade waste agreements.

Dispersion of the Effluent Ovtfall

Outlall

60

outfalls relates largely to the first two years of their operation, that is, August 1991 to August 1993.

Eilluent discharged from the deepwater outfalls undergoes rapid initial dilution, typically within 500 metres of the outfall, before reaching either a level of neutral buoyancy or the ocean surface. Median initial dilu tions, based on hourly near field model results for th e period from 1 March 1991 to 1 March 1994, are given for each deepwater outfall in Table 3. T hese initial dilutions, which have b een verified by direct observations (Pritchard et al 1993, 19966), are one to two orders of magnitude greater than those achieved at the former cliff face outfalls (Caldwell Connel, 1980). Model results also indicate that eilluent plumes from the deepwater o u tfalls remain trapped below the sea surface for more than 80% of the time. Plumes reach the surface w hen the water column becomes unstratified, mainly during winter.

ENVIRONMENT Typical far field plume behaviour is illustrated by the results of a radioisotope tracer experiment conducted from Malabar on June 17-181992 (Figure 4).

On this occasion, initial dilutions were over 1: 1000 and the plume remained submerge d (depth >40 metres) and travelled parallel to sea floor contours to the south with slow subsequent (far field) dilution.

The key oceanographic processes that control the physical dispersion of effiuent off Sydney, including the East Australian C u rrent, coastal trapped waves, internal waves and tides and local w ind-driven curren ts, have been described elsewhere (see Wilson et al 1996; Lee & Pritchard , 1996; Middleton et al 1997).

Some effiuent constituents w ill be dissolved or neutrally buoyant and will therefore travel in an effiuent plume while others will float or sink and therefore travel independent from the plume.

Simulations of settleable sewage particles , based on laboratory measurements (Baker et al 1995) and plume modelling (Wilso n et al 1996) , suggested that sewage particles wo uld be initially deposited in a zone w hich forms a strip parallel to the coast, also with a southerly bias.

This zone of initial deposition , centred at water depths of 60 to 80 metres, falls just within the mid-shelf zone where previous studies (eg: Roy and Thom , 1981; Schneider and Davies, 1995) have indicated that fine sediment particles and associa ted co ntaminants are more likely to accumulate compared to the inner shelf w here the former cliff fac e o utfalls operated. Re-suspension and subsequent transport of sediments containing sewage material was not directly assessed.

Laboratory studies indicated that about three percent (by mass) of sewage effiuent particles would be buoyant in seawater and wo uld rise through at least 1. 7 m etres in 24 hrs (Baker et al 1995).

Most of these floatable particles were less than 52 microm etres in diameter.

Winds w hich could result in landfall of floa ting particles occurred about 20 percent of the time, mostly during the summer months (Wilson et al 1996) .

Fate of Contaminants Contaminants in the plume and in the floating and settling m aterial may be transported out of the region or may acc umulate in se diments or biota.

Various studies examined aspec ts of these fates.

In the water column, monitoring data demonstrated substantial and almost immediate improvements in water quality (reductions in faeca l coli forms, nutrients and suspended

solids concentrations) at cliff-face would be reduced to a very small o utfall sites. of pre-commissioning percentage Trace contaminants were more diffi- levels, while offshore concentrations cult to m easure in the water column. would be an order of magnitude less T hey were measured directly in surface than inshore pre-commissioning levels. waters and in the microlayer (air-sea These predictions were generally interface) when the shoreline outfalls consistent w ith the results of the were operational (Rendell and Espey, 1996) and indirectly in fis h and deployed oysters, both Average daily waste flow before and after commissioning of the deepwater outfalls (Scanes and Rendell , 1996a).

Microlayer studies sought to ID Bond Im North Head address concerns raised by ~ 400 â&#x20AC;˘Malabar J overseas studies (e .g. Cross et al > 1987) that contaminants can concentrate in the at the air-sea ~ , ::nr.:,:.: ':l"U:N interface and can have lethal and Yu,11 sublethal effects on microscopic organisms, such as the eggs and !Average daily suspended solids load larval stages of fi sh . EMP (R endell and Espey, 1993) >'.: 140 results indicated that, while the ~ 120 cliff face outfalls were still ! ,oo operational, contaminant .0 . "' concentrations in the m icroi 60 layer were generally comparable to relatively unaffected areas in overseas studies. Because of this 89/90 9001 91/92 92193 93/iM 94,95 95196 Yfill l finding and the practical difficulties associated with this type of sampling in the ocean, no work was u ndertaken at the outfalls after d eepwater ., comnnssiomng.

In oysters deployed in the D Bond m NorthHead water column, elevated concenâ&#x20AC;˘ Malabar trations of organochlorines were associated with proximity to the cliff-face outfalls w h en they were operational (Scanes and IJ9}3() 9081 91/i,2 92,93 S3J94 94,95 95'98 Voar Henry, 1992). Large decreases in organochlorine concentraFigure 3 Effluent flows and loads from 1989 to tions followed de-commission1996 based on licence compliance monitoring data ing of cliff-face outfalls (Scanes, in press).

Organochlorine concentrations were no longer elevated compared to reference sites. At the deepwater outfall sites, no significant changes were detected in trace metal or organochlorine concentrations in oysters.

At both offshore and inshore sites, no fish exceeded NFA MRLs for organoc hlorine compounds after the deepwater outfalls were commissioned (discussed later).

Fugacity and partition modelling was used to investiN I gate the fa te of specific organic Stanwen Park co ntaminants across vario u s ~km 30 t,(1 ., environmental compartments (water, sediment, fish, etc) Figure 4 Malabar Plum e Behaviour on 17-18 June (Mortimer and Connel, 1995).

1992. Over a period of 26 hrs a labelled portion of the This modelling predicted that submerged plume was tracked and sam pled for some organ0chlorine contamination 36 kms. Faecal coliform densities are geometri c means (from Pritchard et al 1993) of fi sh at inshore locations

I

I

~

~

~

~MM)

I

/eurrent

â&#x20AC;˘

WATER MARCH/ APRIL 1997

31

ENVIRONMENT contaminants in fish studies (Krogh and Scanes in press).

The recovery at the old cliff-face outfall sites was mainly reflected in reduc tions in the co ncentrations of organochlorines and lead measured in the flesh of red morwong (see Figure 5) and deployed oysters.

In the sediments, the proportion of fine grained sediments has increased at sampling sites near Malabar deepwater outfall, decreased at North Head outfall si tes and remained essentially constant at Bondi o utfall sites (Otway et al 1996). However, no changes in concentrations of organic carbon could be attributed to the commissioning of the deepwater outfalls (Gray, 1996).

A propo rti on of floatable sewage particles will still be stran ded on beaches. H owever, concentrations of grease in sand at most beaches near the old outfalls (from South Curl Curl to Malabar) have decreased since commissioning of the deepwater outfalls and there is no evidence of an increase in beach grease at more distant beaches (Robinson et al 1996).

Impacts on Marine Ecosystems At the deepwater outfall sites, the variety of habitats potentially affected by effluent include deepwater reefs, soft sediments and overlying waters . EMP studies at tempted to characterise biological assemblages within each of these habitats. Changes in these assemblages at outfall sites, following commissioning of the outfalls, were compared with the 'natural variability' observed at a number of distant control or reference locations.

During EMP monitoring there were no sustained effects of the outfalls on the overall diversity (number of species) of biological communities found to be due to the operation of the deepwater outfalls. However, the outfalls have caused both increases and decreases in the abundance of a number of components of the soft bottom, planktonic and demersal fish communiti es near the outfalls (Scanes and Rendell (eds), 19966).

Eleven species of fish (out of 65 analysed statistically) showed sustained changes in abundance arou nd t he deepwater outfalls - so me species increased in abundance w hile others decreased. Significant changes in abundance were found for five types of fish larvae near the deepwater outfalls.

Again, increases and decreases were found with no obvious pattern among outfalls. The types of larvae which changed were different from the adult fish which changed. This suggests no effects of altered recruitment at the time of sampling. T here was no evidence that t h e presence/absence, abundance or 32

WATER M ARCH/APRIL 1997

proportional representation of deformed larvae were higher in Sydney than at far control l ocations (Terrigal or Greenwell Point).

Abundances and species assemblages of p hytoplankton were not assessed in the EMP or any related studies although no significant changes in chlorophyll-a levels (used as a surrogate measure of phytoplankton abundance) that were co nsistent with an effect of the outfalls were detected following the commissio ning of t he deepwater o u tfalls.

However, mean chlorophyll-a concentrations at both reference and outfall sites were ge nerally higher after commissioning of the outfalls.

There were no significant changes in the numbers of species which comprise the assemblages living in sandy areas ('soft- bottom benthos'). There were, however, changes in abundances (bo th increases and decreases) of many taxa and the composition of species. A slight reduction in species richness of organisms living attached to deepwater reefs occurred near the North Head outfall, but no dominant taxa showed changes in abundance.

At the former cliff- face outfall sites, the rocky reef habitats are typically dominated by medium sized, attached

or slow moving animals and attached algae with fish in the overlying waters.

Other studies (Banwell, in prep) have shown that, followi ng the diversion of effluent offshore, the impacted biological assemblages of intertidal areas near the cliff- face outfalls recove red to become much more like other intertidal assemblages along the rest of Sydney's coastline. It is interesting to note that the diversity and abundances of subtidal assemblages of fish and benthos near the cliff face outfalls were, in ge neral, markedly unaffected by sewage discharge, despite the fact that the discharge had been occurring there for decades (Smith and Lincoln-Smith, 1993; Underwood et al 1993; Chapman et al. 1995).

Impacts on Human Utlllsatlon of Marine Resources At almost all Sydney beaches bathing waters are now suitable to swim in and beaches are free from readily visible sewage material for more than 90 percent of the time. The frequency and intensity of visible and bacterial sewage pollution has decreased with t he comm1ss10ning of the deepwate r outfalls, particularly at those beaches close to the former cliff face outfalls.

Table 1 Sydney's deepwater outfalls Outfall North Head Bondi Malabar

Water Depth (m)

Outfall Length (m)

Diffuser Length (m)

Outfall Capacity (Ml/d)

Average Flow (Ml/d)

60 60 80

290 0 1700 2900

765 510 720

2400 700 2250

385 165 490

Table 2 Composition of effluent discharged from Malabar deepwater outfall Effluent Constituent Concentrations 1.5 Solids (m&fL) Suspended solids Grease (oil and grease)

133 22

Nutrients (m&/L) Ammonia N Metals2 (u&fL) Arsenic Cadmium Chromium Copper Lead Mercury Nickel Selenium Silver Zinc

27

n.d. {<5) n.d. {<5) 32 128 14 n.d. {<0.5) 34 n.d. (<5) 6.0 172

Organochlorlnes 2 (u&fL) Chlordane Dieldrin Heptachlor Lindane PCBs Others3

0.04 0.02 0.04 0.02 n.d (<0.1) n.d. (<0.01)

Polycyclic aromatic hydrocarbons 2 (u&fL) Total PAHs4 5.0 Others (u&fL) Cya nide Phenols

n.d. (<10) 79

1 Median concentrations from licence compliance data for 01/04/94 to 31/03/95. Solids were measured daily while others were measured as 24 hr composites every 13 days.

2 Total concentrations.

3 Aldrin, BHC, DOD, ODE, DDT, endosulfan, endrln, hexachlorobenzene, methoxychlor.

4 Calculated by adding the concentrations of individual PAH compounds (not detected â&#x20AC;˘ 0).

5 n.d. â&#x20AC;˘ the median value was not detected.

Table 3 Median initial dilutions North Head Bondi Ma labar

Surface Plume

Trapped Plume

All Conditions

817 1193 636

349 414 513

379 456 532

ENVIRONMENT Altho ugh highly diluted efflue nt (contain ing faecal bacteria) and sewage grease may, on occasions, find its way to Sydney beaches, othe r pre- existing sources (e.g. smaller existing cliff face outfalls and stormwater) now stand out as issues of perhaps greater concern.

The reduction in the frequency of visible sewage pollution following comm1ss10ning of the deepwater outfalls is illustrated in Figure 2.

In fish there was no evidence that the comm1ss1oning of the deepwater outfalls has led to an increase in levels of chemical contaminants to the extent that they are of concern relative to the Nati onal Food Au thority Maximum R esidue Levels (NFA M RLs) . If N FA M RLs are used as a guide, then, based on the mean level o f contamina n ts fou nd in fish associated w ith Malabar deepwater outfall (which discharges the greatest load of most contamina nts), these fish are generally safe to eat. After the commissioning of the outfalls, no fish was found to have organochlorines p resent above the MRL although a small percentage of fis h fro m both Sydney and distan t cen tral locations were fou nd to contain some trace metals at concentratio ns above relevant M RLs. T he frequency of detections of orga n ochlo rin es increased slightly (possibly reflecting improved analytical techniques) although the proportion of fish with tissue concentrations of organochlorines w hi ch were high (greater than NFA MRLs) act ually decreased to zero following the commissioning of deepwater ou tfalls.

All contaminan t concen tratio ns observed in red morwong at cliff-face o utfall sites after decommissioning of the outfalls were 'low' when compared with N FA MRLs (Krogh and Scanes, in press) . When cliff-face outfalls were in use, me rcu ry, chlordane, heptachlor epoxide and H CB were som etimes found at concentratio ns greater than N FA M RLs in fis h caught near cliffface o utfalls (Lincoln Smith and Mann,

Beach and bathing water quality have dramatically improved since efflu ent was diverted offshore to the deepwater ou tfalls, though some residual problems remam .

EMP studies have sh own t hat contamination of sediments and biota in the vicinity of the new outfalls did not change to an extent that can be readily measured by the tec h nology and methods utilised in these studies.

It appea rs fro m the computer modelling of plume behaviour and the studies of biota and sediments that the enhanced rate of dilution and dispersion has resulted in a decreased likelihood of any given organism or area of sediment encountering (and therefore accumulating) high loads of a contaminant, but concomitan tly there has been an increased likeli hood of more organisms accumulating small amoun ts of contaminants.

Ecological studies in the vicinity of the cliff face ou tfalls and the deepwater outfalls have shown that there have been some ecological impacts around the deepwater outfalls and some recovery of t he inte rtidal assemblages p revio usly affected by the cliff face outfall. T he specific causes o f the changes near the deepwater outfalls are unknown. There was little consistency among outfalls and no apparent relationship between abundances of predator and prey groups. T he changes do not appear to be accounted for by the p resence of toxicants. Based on effiuent quality data and initial effiuent dilutions, ANZECC (1992) guidelines for the protection of aquatic ecosystems h ave easily been met

Chlordane

Dleldrln

- + - CONTRO L

- •-

1989a; McClean et al 1991).

Levels of faecal bacteria in offshore waters at and south of the deepwater outfalls (ie. locations in the path of the effluent plumes) necessitate prope r storage and preparation of fish caught in this area if the intention is to consume them raw.

Discussion

OUT FALL

-+- CONTROL

- • -- OUTFALL

0 .25 ~ - - -- - - -- ~

o .o s o ~ - - - - - - -- - -

0.20

o .04s

-

~0.1 5 Cl

E 0 .10 0 .05

1

~

r

,

~0.036

ci

E 0.024 0.012

~· ·

0. 00 .__2..__...__...... ~___.!i!_ l;:!..__., ..__.L.,----L ..--'

i

~

! ~ !- ~ Date

!

Figure 5 Mean chlordane and dleldrin concentrations In red morwong muscle tissue for all control and all outfall sites

after initial dilution in recent times (1994/95). Likewise, contaminant concentrations in sediments near the deepwater outfalls were also below the levels considered to have the potential to cause biological effects.

These changes were observed at sites close to the outfalls. At this stage it is unclear h ow far the impacts may exte nd. But it is appare n t that the observed changes are likely to extend considerably less than 10 to 20 kilometres from the outfalls, as this was t he distance to control sites. This view is suppo rted by the observation that changes at one outfall frequen tly diffe red from those at adj acent outfalls, yet the outfalls were o nly seven to eight kilometres apart. However, fu rther studies are being implemented to establish w hether the changes already identified persist and whether other chronic effects develop in the longer term.

Despite the generally good performance of the outfalls, a numbe r of residual enviro nmental issues have emerged. Some of these are associated with the deepwater outfalls w hile others are common to a broad area of NSW coastal waters. Pritchard et al (1996a) describe the ways in which these issues are being addressed.

Remaining deepwater outfall issues include: • potential for accumulations of sewage particles and associated con taminants in offshore sediments; • unexplained m inor c hanges in ab undances of certain bottom dwelling organisms and free swimming fis h near ou tfalls; • occasional p resence of sewage grease on beaches • faecal pathogens in sewage plumes.

Further gene ral marine issues which have been raised or highlighted by the EMP, but not attributed specifically to the operation of the deepwater outfalls, include : • occasional exceedances of N FA MRLs for some trace metals in fish from NSW coastal waters; • possib le n utrient enrichme n t of coastal waters and its effect on p hyto plankton growth (algal blooms); and • beach and bathing water pollution originating from stormwater sources and the remaining cliff- face outfalls discharging primary treated sewage.

Further monitoring and investigations to assess continued performance and to alert us to the development of possible longer term effects of t he deepwater outfalls include the monitoring of sewage effiuent, simulations of plume behaviour, the monitoring of ocean beaches and the regular monitoring of the quality of offshore sediments and the abundances of the organisms which are found living in and on these sediments.

WATER MARCH/APRIL 1997

33

ENVIRONMENT Concluding Remarks The legacy of the EMP is a better understanding of Sydney's coastal environment and a baseline data set against which the future environmental performance of the deepwater outfall systems can be assessed.

However, the results of the EMP contribute to just one element of a broader debate about effiuent management which must be considered within the context of the entire water cycle.

Over the last few years the NSW EPA, and many others, have concluded that we wiU have to regard water and nutrients in sewage as increasingly valuable resources which we should make concerted efforts to recover. Already, new legislation (the Sydney Water Board [Corporatisation] Act, 1994)

places great emphasis on re-use of effiuent and minimising the quantities of pollutants discharged to the ocean and other watenvays.

The NSW Government has recently announced a public inquiry that will seek solutions to effiuent management problems in coastal NSW. The Effiuent Management lnqui1y will assess the 'environmental costs' of ocean outfalls and other effiuent disposal schemes and will consider options for further demand management and re-use.

Acknowledgements This paper draws on the EMP Final Report Series particularly Volume 1: Assessment of the Deepwater Outfalls (Pritchard et aL, 1996a), which, including its appendices, contains 194 pages.

Paul Rendell's constructive criticism of an early draft of this paper is appreciated. Muriel O'Farrell produced the graphics for this article. The principal EMP contractors were Australian Water and Coastal Studies Pty Ltd and NSW Fisheries Research Institute. EMP pilot studies and much of the initial program design were undertaken by Sydney Water Corporation (then as Sydney Water Board) and its consultants.

Throughout its life, the EMP was reviewed principally by the EMP Technical Review and Advisory Committees.

References ANZECC (1992) Australian Water Quality Guidelines for Fresh and Marine Waters, Australian and New Zealand Environment and Conservation Council, Australia.

Baker EK, Harris PT, Kensett-Smith B, Bagster D F and Nobbs M N (1995) Physical properties of sewage particles in seawater, Mari11e Pollution Bulletin 30, 247-252.

Banwell K (in prep) Effects of Sewage on Intertidal Assemblages, MSc Thesis, University of Sydney (Sydney).Caldwell Connel Engineers (1980) Analysis of Oceanob>raphic Data and Review of Ocean Outfall Design Concepts. Report to Metropolitan Water, Sewerage and Drainage Board, Sydney.

Chapman MG, Underwood AJ and Skillctcr G

34

WATER MARCH/APRIL 1997

A (1995) Variability at different spatial scales between a subtidal assemblage exposed to the discharge of sewage and two control assemblages, Journal of Experimental Mari11e Biology & Ecology, 189, 103-122.

Cross] N, Hardy J T, Hose] E, Hershelman G P, Antrim L D, Gossett R Wand Recelius E A (1987) Contaminant concentrations and toxicity of sea-surface microlayer near Los Angeles, California., .1vlari11e E1wiro11.Res., 23, pp 307-323.

Gray L (1996) 'Contaminants in Sediments'. In: $canes, P. and Rendell, P. (Eds). Sydney Deepwater Outfalls Environmental Monitoring Program, Final Report Series, 4: Trace Metals and Volume Organochlorines in the Marine Environment. Environment Protection Authority. Sydney.

Green R H (1979) 'Sampling Design and Statistical Methods for Environmental Biologists'. Wiley & Sons ( New York) Fairweather P G, 1990 Sewage and the biota on seashores: assessment ofimpact in relation to natural variability. E11viro11111e11tal J\lfo11itoring a11dAssessme11t, 14, 197-210.

Krogh M and $canes P R. (in press, 1997) Organochlorine Compounds and Trace Metal Contaminants in Fish Near Sydney's Ocean Outfalls. Marine Pollution Bulletin Lee R. Sand Pritchard TR (1996) Dispersion of effiuent from Sydney's new deepwater outfalls Part 1: Ocean Processes. In, 'Coastal and Estuarine Studies (50),: Pattiaratchi (Ed.) Mixing in Estuaries and Coastal Seas' American Geophysical Union, pp430-438.

(Washington, DC) Lincoln-Smith M P and Mann R A (1989a) 'Bioaccumulation in nearshore marine organisms. Organochlorine compounds in the red morwong Cheilodactylus fuscus, around Sydney's three major sewage outfalls' State Pollution Control Commission, Sydney Lincoln-Smith M P and Mann R A (1989b) 'Bioaccumulation in nearshore marine organisms. Organochlorine compounds in the rocky reef animals near Malabar sewage ocean outfall' State Pollution Control Commission, Sydney McLean C, Miskiewics A. and Roberts E (1991) Effect of Three Primary Treatment Sewage Outfalls on Metal Concentrations in the Fish Cheilodactylus fiscus Collected Along the Coast of Sydney, Australia. Mari11e Poll11tio11 B11llcti11, 22(3), 134-140.

Middleton], Cox D and Tate P (in press, 1997) The Oceanography of the Sydney Region. ,V!arine Poll11tio11 Btilfeti11.

Mortimer M R and Connel D W (1995) A model of the environmental fate of chlorohyrocarbon contaminants associated with Sydney sewage discharges. CftemospfteJ'r!, 30(11), 2021-2038.

Onvay NM, Ling] E, McVae TA and Walker A R (1996) Soft-Bottom Community. In: $canes, P. and Rendell, P. (Eds). 'Sydney Deepwater Outfalls Environmental Monitoring Program, Final Report Series, Volume 5: Impacts on the Marine Environment Protection Ecosystems' Authority. Sydney.

Pritchard T R, Lee R S and Davison A (1993) Sydney Deepwater Outfalls: In Situ Observations of Plume Characteristics. 11th Australian Conference on Coastal and Ocean Engineering, Townsville' Institution of Engineers Australia, Canberra Pritchard TR, Rendell P, Scanes P and Philip N (1996a).

Sydney Deepwater Outfalls Environmental Monitoring Program, Final Report Series, Volume 1: Assessment of the Deepwater Outfalls. NSW Environment Protection Authority, Sydney, Australia.

Pritchard TR, Lee RS and Davison A (1996b) Dispersion of effiuent from Sydney's new deepwater outfalls Part 2: Observations of

Sewage Plume Behaviour: Winter and Summer Examples. In, 'Coastal and Estuarine Studies (50),: Pattiaratchi (Ed.) Mixing in Estuaries and Coastal Seas' American Geophysical Union, pp 439-452 (Washington DC).

Rendell P S and Espey Q (1993). Sydney Deepwater Outfalls Environmental Monitoring Program, Pre-Commissioning Report Series, Vol 8: Microlayer. EPA Sydney.

Robinson L, Heggie A and Coade G (1996).

Sydney Deepwater Outfalls Environmental Monitoring Program, Final Report Series, Volume 3: Water Quality. Environment Protection Authority. Sydney.

Roy PS and Thom BG (1981) 'Cainozoic shelf sedimentation model for the Tasman Sea margin of southwestern Australia' Geological Society of Australia Special Publication 18, 119-136. $canes PR and Henry G W (1992) Bivalve and Morwong Bioaccumulation, EMP Pre-commissioning Report Vol. 8, Environment Protection Authority, Sydney. $canes P R and Rendell P (Eds). (1996a).

Sydney Deepwater Outfalls Environmental Monitoring Program, Final Report Series, 4: Trace Metals and Volume Organochlorines in the Marine Environment. Environment Protection Authority. Sydney. $canes P R and Rendell P (Eds) (1996b).

Sydney Deepwater Outfalls Environmental Monitoring Program, Final Report Series, Volume 5: Impacts on the Marine Ecosystems. Environment Protection Authority. Sydney.

Schneider PM and Davey SB (1995) Sediment Contaminants off the Coast of Sydney, Australia: A Model for their Distribution.

Marine Poll11tio11 B11/leti11, 31, 262-272.

Smith A and Lincoln Smith M (1993) Changes to Communities of Reef Fish Adjacent to the North Head and Bondi Cliff-face Sewage Outfulls Following Decommissioning, Final Report to Water Board, Sydney, The Ecology Lab., Sydney.

Wilson] R, Cox DR, Walker] W, Howden M I, Couriel E Dand Lee R (1996). Sydney Deepwater Outfalls Enviromnental Monitoring Program, Final Report Series, Volume 2: Sewage Plume Behaviour.

Australian Water and Coastal Studies Pty Ltd. Sydney.

Underwood A J (1991). Beyond BACI: Experimental Designs for Detecting Human Environmental Impacts on Temporal Variations in Natural Populations. Australian jo,mwl of Marine a11d Freshwater Researcf1, 42: 569-587.

Underwood A J (1992). Beyond BACI: The Detection of Environmental Impacts on Populations in the Real, but Variable, World.]011mal ofExperime11taf Marine Biology a11d Ecology, 161: 145-178.

Underwood A J (1993) The mechanics of spatially replicated sampling programmes to detect environmental impacts in a variable world. A11s1ralia11 Joumal if Ecology. 18, 99116.

Underwood AJ, Chapman MG, Howitt Land Skilleter G A (1993) North Head Ocean Outfall Project, Final Report to Water Board, Sydney, Institute of Marine Ecology, University of Sydney.

Author Tim Pritchard is Manager of the Marine Watm Unit of the EPA of NSW (Locked Bag 1502, Banksto,vn, 2200), He

graduated from Southampto11 U.K. and gained his MSc in geophysics at Syd11ey.

After research in mari1te scie11cefron1 1981 to 1

1990 he joined the NSW EPA (then the

SPCC) where he specialises in oceanography.

ENVIRONMENT Introduction There are currently more than 190 saline disposal basins throughout the Murray Basin. They va1y in size from a few hectares serving individual farms to

aquifer dispersion. Where instability does occur, 'fingers' of dense saline fluid penetrate deep into the aquifer, over distances much greater than those attributable to diffusion alone.

Application to the Murray Basin

TECHNICAL NOTE

SALINE DISPOSAL BASINS KA Narayan very large basins serving large regions and land management schemes.

Collectively receiving over one million tonnes of salt per year, they arc likely to remain a cost-effective means of reducing salt flow to the [liver Murray for the next century.

The environmental impacts of such basins are largely unknown. Concerns have been raised that disposal could enhance release of salt into aquifers, salinise surrounding land and ultimately return to the river system.

An example of a computed vertical profile, one of a time series, is given in Figure 1.

Achieving Basin Stability Initially a model called SUTRA (saturated-unsaturated transport) developed by Voss (1984) for the U S Geological Survey was chosen for the investigation. Further work, however,

Disposal System Dynamics In most disposal basin systems, a fluid of higher density overlies groundwater of less density. Results suggest that this may be unstable since the higher density fluid would tend to sink through the process of convection.

Whether or not this occurs depends on basin-scale parameters such as permeability, porosity, basin salinity and

The first application of the modelling was at Lake Tutchewop, Victoria, now used as a saline disposal basin in the Riverine Plain of the Murray Basin, midway between the townships of Kerang and Swan Hill.

Before its diversion to the lake, the Barr Creek delivered an average of 180,000 tonnes to the River Murray each year!

Concentration profiles computed for the Lake Tutchcwop system were compared with hydrochemical data at the site for the period 1989 to 1993 and were in good agreement. The leakage effects of the current disposal scheme are seen to be limited to the top 3-4 m below the basin. Model predictions (Simmons & Narayan 1996) show that even by 2015 saline leakage would be confined to within 10 m of the lake bottom, as shown in Figure 2. This particular system is inherently stable due to the low permeability of the Shepparton clay formation which underlies the basin.

Conclusion

Aims of the Project In a project funded by the MurrayDarling Basin Commission, CSIRO's Division ofWater Resources, in collaboration with the CSIRO Centre for Environmental Mechanics, the Centre for Groundwater Studies and the Australian Geological Survey Organisation, investigated the hydrological dynamics of disposal basins and the factors favouring stability.

The primary objectives were: • to develop criteria (stratigraphic and climatic) for siting disposal basins • to develop a user-friendly model for simulating the processes in regions containing disposal basins • to develop management and monitoring strategies to establish the optimum protocol for salt storage, while minimising effects on the regional groundwater system.

that this approach would be a highly reliable way of predicting long-term behaviour. Just as importantly, it would be a valuable tool for deciding which sites were suitable.

Figure 1 Computed concentration profiles of a Hele-Shaw cell, highlighting 'finger' formation in a vertical slice

A clearer picture of the governing hydrodynamics and the management criteria required has been obtained from this research. The SUTRA model can now be readily applied to many saline disposal systems, both for current management and for predicting their future environmental impact. In particular, it will prevent a recurrence of the siting errors of the past and identify more hydrologically appropriate locations for future disposal.

References revealed the need for a more versatile and complex spatial mesh, and the team developed an interface between SUTRA and the CSIRO system FEM CAD. (Buia et al 1994). Following laboratory trials by the CSIRO Centre for Environmental Mechanics using Hele-Shaw cells and Rayleigh number analysis, the factors driving the fingering behaviour were characterised. Both the processes of free convection (driven by bouyancy) and forced convection (driven by hydraulic gradient) were considered.

Given known basin and aquifer properties, the work showed that it was possible to predict the onset of instability. Indeed, laboratory trials suggested

Buia M, Simmons CT, Narayan KA (1994) Interfacing the FEMCAD generated finite clement mesh with the groundwater flow and solute transfer model SUTRA. CSIR.O Division of \Vatcr Resources Divisional Report 94/4.

Simmons C T, Narayan KA (1996) Mixed convection processes below a saline disposal basin.J11l efHydrology (in press) Voss C I (1984) SUTR.A: A finite-clement simulation model for saturated-unsaturated fluid density-dependent groundwater flow with energy transport of chemically reactive single species solute transport. US Gcol.

Surv. Water Resource Invest. Rep. 844369.

Author Dr Kumar Narayan is at the CSIRO

Division ofVVater Resources P1v!B 2, Glen Osmond SA 5064 1

WATER MARCH/APRIL 1997

35

BUSINESS

WATERLOG D Cummins Abstract South East Water Limited, one of the retail water companies supplying water and sewe rage services to Melbourne, Victoria, has developed a

customer information and work management software system called 'WaterLog'. It is used by the Field Services Division to record unplanned and planned supply restoration work, often generated from customer calls.

T he system also supports the contractors carrying out the work, processing

all works on screen from job commencement to final invoice. Many of the complex paper systems have been eliminated, and the system has been well accepted by all levels of personnel.

Introduction South East Water Limited (SEWL), was formed in January 1995 as the provider of water and sewerage services to the South East region of Melbourne.

It is one of three retail water companies whic h provide services under a "Licence to Operate" arrangement as monitored by t he Victorian Government. As the key part of reform of the Metropolitan water ind ustry, SEWL operates in a "competition by comparison" environment with other Metropolitan water companies. The area covered by SEWL is shown on Figure 1, and the company services some 1.4 million customers, in 568,000 properties. It operates 7,500 km of water pipelines and 6000 km of sewer mains.

Within SEWL, Field Services is the division responsible for operating the water and sewerage systems. All field based repair work is initiated from Field Services (often from c ustomers' telephone calls) and then carried out by various contractors (Thiess Contractors/ Siemens are the principal contracto rs).

WaterLog-Why?

Figure 1 The front screen for Waterlog

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Soon after indep endent operation commenced, Field Services Division evaluated a number of "off- the-shelf' management products but failed to find a system whic h me t the exacting requirements of SEWL. In co nsequence th e "WaterLog" computer system was developed "in-house". In addition to a comprehensive customer call and work management system, WaterLog provides many other benefits not fou nd in alternative packages.

Waterlog was introduced during 1995, and has already changed significantly from the initial product.

Ongoing changes and development are expected as the business changes rapidly and new requirements are identified.

The system has been developed fro m the standard Microsoft range of products and it has been purposely designed to provide an easy and friendly interface for all users . This is best demonstrated by the reactions of a large section of Field Services personnel who are not regarded as sp ecifically computer-skilled, yet all remark without exception how easy it is to use WaterLog to enter new works and query existing work information.

WATER MARCH/ APRIL 1997

37

BUSINESS The Communications Centre

Contracting

The "focus" of Field Services operations is the Communications Centre.

The Centre uses WaterLog as the provider and recorder of information, and it is here where all unplanned works are logged as a result of inbound customer telephone calls. During daylight hours, operators with computer and customer service skills use WaterLog continuously to enter up to an average of100 new jobs per day, in addition to providing work progress to other customer inquiries. Figure 2 is the front screen where all actions commence. All new works sites are validated against a Melways (Melbourne street directory) database to ensure accuracy for crew allocation. Figure 3 shows an example of the work input screen with information including street history to assist the telephone operator to accurately diagnose work requirements. Special consideration is given where water mains need to be turned off for immediate work. A separate "waterofP' screen shows comprehensive details of all streets effected in a "shut-off'' area and anticipated supply restoration times. All this information can then easily and accurately be conveyed to our customers. Figure 4 is an example of a call details screen which provides general details after a job has been logged, and from which all subsequent actions commence.

In addition to the central grouping of PCs in the Communications Centre, other "WaterLog PCs" are located throughout the Field Services office to allow the various work authorisation and administrative functions to be completed. All PCs are connected via the office LAN and full back-up procedures and contingency plans arc available to be used in an emergency.

As well as storing customer call and history information, the system is also used by SEWL's civil contractors (Thiess) to manage, schedule and allocate all work. Paperwork has all but been removed from the lengthy works completion process, with even regular contractor invoicing produced on screen. A final print of the completed works invoice is made for visual and approval purposes only.

"Sign-off'' at various stages of the completion process for each job is done on screen using a multi level supervisor (password-controlled) system. SEWL supervisors and administrative officers all "sign-off' on each job to ensure that works are in accordance with contract specifications and that the appropriate administrative processes are in order.

All actions are fully documented to allow follow up of who approved what, why and when. All work can pass back and forth on screen between Thiess and SEWL until final invoicing is complete.

Reporting A significant part of SEWL Operating Licence requires comprehensive reporting of works impacting on customers. It would be reasonable to expect these requirements to be increased in the future. A large number of standard queries from WaterLog arc produced on a regular basis to support the Operating Licence requirements.

The ability to do ad-hoc queries on all types of recorded information is also a major benefit of the WaterLog system.

In addition to external reporting, internal reporting of data is required to allow other internal divisions within SEWL to carry out their specific functions. In particular, the Assets & Engineering Division's asset management group are regularly supplied with asset data. All work information 1s

Melbourne

Port Melbourne

Dandenong Port Phillip Bay â&#x20AC;˘Frankston

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attached to individual assets and WaterLog is able to supply costing and parts attributable to each asset where work has been carried out.

This infonnation forms the basis of longer term analysis data and is particularly applicable for replacement projections.

To ensure the ongoing success of the maintenance contract, and the very successful position SEWL has as the leader in the provision of service, summarised work status information is critical for management viewing to allow early detection of potential work management problems. WaterLog is designed to provide features to support this observatory role and it does so extremely well. Daily graphs of numbers of work items entered give early trends to allow management to follow up and action. Restrictions in the processing of each job as it moves from start to completion through WaterLog can be identified, again allowing management to act prior to major problems being created.

A recent enhancement allows for managers and supervisors to constantly view a summary list of the recent jobs entered into the system. Whilst continuing with normal daily work this WaterLog feature allows for any monitor works items manager to recently added by telephone operators.

The Future After 12 months' service, WaterLog has been found to be extremely beneficial to the success of SEWL. WaterLog has now been demonstrated to a number of Water Authorities across Australia, and positive responses have been received.

The next development stage involves recording and sending back to WaterLog remote data from field locations. This will enable real time data to be available in the Communications Centre and will speed up the job completion process. Efficiencies are expected to be achieved through the further reduction of contractor paperwork and the need to pass information through various people prior to inputting of completed information into WaterLog. The "road ahead" is an exciting one, as technology is quickly developing. It is the intention ofSEWL to take advantage of technology where technology can be shown to be of benefit to our business.

Author MAP OF SOUTH EAST WATER AREA

South East Water area 38

WATER MARCH/APRIL 1997

David Cummins is Manager, Communications Centre of SEWL. He was previously with Melbourne Water as Manager Service Assurance, with 25 years experience in the water industry.

WASTEWATER Summary Activated biosolids arismg from aerobic treatment processes are in some installations dewatered directly by belt press or centrifuge. The results in terms of dewatcred cake solids from installations around Australia have shown a great deal of variability. Comparing the dewatercd cake solids against the percentage of non-volatile solids (ash) in the dcwatered cake has established a strong correlation. This allows specifiers and suppliers of dewatcring equipment to better characterise the biosolids, in order to form a basis for agreed performance of the equipment.

A simple observation method is also proposed, which allows a quick evaluation of whether the dcwatering device is close to the optimum performance on a particular biosolids mass.

The data is based on conventional belt press performance. However, it is also applicable to conventional centrifuges.

A new generation of belt presses and centrifuges offers higher performance, but this is still within the expected performance band of the data.

Introduction Activated biosolids processes arc currently in fashion around the world, and particularly in Australia, due to our relatively low energy costs. These processes include intermittently decanted aeration, continuous aeration, secondary activated biosolids processes, and biological nutrient removal. All of these processes result in excess biosolids. Some are thickened prior to anaerobic digestion but most arc directly dewatered for disposal to landfill or for further processing, eg. by incineration. A wide variation in the solids content of such biosolids cakes, ranging from 11 % solids to 20% solids, has been encountered at plants of similar process design, even using identical dcwatering equipment, at different installations. The physical nature and appearance of the cake can also be the same for very different solids contents (Bane, 1990).

The variety of treatment processes in use today, as well as variable influents, can result in varying ash contents of the cake, and this value is often not stated or known at the pre-construction phase. This paper proposes the use of the non-volatile (ash) solids content of the dewatered cake as an indicator of the attainable dewatered solids content of a particular hiosolids population. The ash content of the filter cake, rather than that of the feed suspension to the dewatering plant, is used since dissolved solids in the liquid phase can provide variable values through the treatment process. If determined it can enable a

DEWATERABILITY OF

ACTIVATED BIOSOLIDS I H Bane better estimate of the dcwatering potential to be established.

Discussion Physical appearance. A factor which is often not realised by engineers working purely on a theoretical basis, is that even though the solids contents of the filter cake might range through a wide set of values, the appearance and the handling characteristics of a well dcwatcrcd biosolids cake arc often virtually identical for a 11 % solids cake compared to an 18% solids cake. This is particularly so in the case of the belt press, where the shearing action and the compressive processes produce a cake which is easily handled and of a dry appearance.

Simple test. A simple but reliable test of the dcwatering efficiency of a particular system can be made by observing the cake as it discharges from a belt press. If it is of a dry, crumbly appearance, and a sample when compressed in the hand only produces a few drops of moisture, then it is well dewatered.

High solids contents. Anecdotal evidence suggests that in some countries, such as China, the attainable cake solids in an activated (aerobic) biosolids process is in excess of 20% solids, however, this data has not yet been confirmed by the author. It is however, believed that the high proportion of industrial wastes in the influent to the treatment works, can raise the ash content of the cake, and therefore the solids content. Also, some plants dosed with metal ions, or lime, can have a higher biosolids ash, and a few such plants exist in Australia, particularly in Sydney. Biological Nutrient Re1noval plants also appear to produce higher cake solids.

Getting More Predictable Results In the past there have been instances

where dewatering equipment suppliers have been penalised due to the actual plant dewatered biosolids cake solids content falling below an arbitrarily fixed design figure. A survey has been conducted and the results show that if the ash content is known prior to installation, the results will fall within a narrower band, and the performance of the equipment can be predicted more accurately.

Table 1 shows a summary of the data from a number of individual plants.

The majority of the results were with one manufacturer's range of belt presses, however, those from other manufacturers' eqipmcnt are included.

The results are a combination of data taken from grab samples on operating plants which arc not necessarily optimised, as well as data from acceptance tests, where the equipment has ben optimised by skilled operators.

The results expressed in graphical form, (Fig.1), show a good correlation between the non-volatile solids (ash) content and the attainable cake solids.

The scatter in results can be attributed to the fact that some of the plants were not optimised (as described above) and variations in the selection of the equipment, as well as the design of the individual piece of equipment., and its design capacity. Most designs of biosolids dcwatering equipment do not have an absolute maximum capacity, and the operating point for the equipment could be above or below the optimal capacity of the dewatering device. However, the normal range of commercial loadings usuall)' results in a variation of 1 or 2 percentage points in cake solids when the throughput is reduced, unless the dewatering plant is heavily overloaded.

In general, the processes employed in the treatment plant do not appear to have a direct measurable affect on the attainable cake solids, except that when dosing with metals is part of the treatment process this can result in a higher WATER MARCH/APRIL 1997

39

WASTEWATER Table 1 Survey of dewatering of aerobic biosolids Supplier

Site

Cake Solids % Ash Content % Notes

Terna Boulder Bay, NSW Anglesea, Vic Supaflo Su paflo Toro nto, NSW Diemme Gibson Island, QLD Supaflo Wacol,QLD Logan holme , QLD Supaflo Loga nholme (New plant) Supaflo Cai rns So uth, QLD Supaflo Su paflo Cairns North, QLD Supaflo St Marys, NSW Terna Coombabah, QLD Diemme Merri mac, QLD YC Merri mac BNR , QLD Rottnest, WA Terna Supaflo Ed monto n, Qld Batea u Bay Supaflo Port Macquarie , NSW Alfa-Laval *

11.35 13 .8 15.86 12.5 13.7 18 .3 15.7 14 13 16.85 10 13 15 11.87 12 14 11.7

15.54 29.8 33.84 10 .5 10 .35 40.6 33. 3 19 25 .5 29 .4 19 18 10 13.21 21 27 23.3

Average

13.8

24.8

No industrial or dosing No industria l or dosing No industrial or dosing Some industria l Some industrial Some industria l, 1987 Some industrial, 1995 Residential Residential Some industria l, BN R Reside ntial Reside ntial Residential SBR Holiday Resort Residential Coastal - little industry Coastal-lit tle industry

* Gravity table, t hen centrifuge

ash content of the cake. As discussed above, a high incidence of industrial influent can have a similar affect.

Biological Nutrient R emoval processes appear to produce quite a good cake, as do some intermittent processes incorporating aerobic final digestion .

Dewatering of anaerobically digested biosolids is a well established technology.

R esults from a number of plants in Europe are shown in Figure 2. When plotted on the same axes as Figure 1, they show a similar correlation between the cake solids and the ash content.

Polymer Dosage

New Generation Devices The latest designs of high solids belt presses and centrifuges (Sernagio tto, 1996: R etter and Schilp, 1994) can achieve higher solids contents than those indicated by the regression line of Figure 1. The diaphragm type filter press can achieve similar results. These types of equipment are generally of the order of twice as expensive as conventional equipment, and would only be used in Australia in instances w here the small d ifference in water removal is significant in term s of disposal costs.

In Australia, w here landfill and further treatment such as dosing with lime for stabilisation is currently used, and land disposal costs are an o rder of magnitude less than those in Europe and the Americas, the small difference in water content has to date not justified the cost of the new ge neration of dewatering equipment.

A secondary factor in the influence of the ash content of the cake is that a cake Conclusion A correlation between ash content with a higher ash content will require an apparently lower polymer dosage rate. and dewaterability of activated biosolids This is due to the fact that the non- from aerobic processes has been estabvolatile solids generally have a lower lished, and can now be used as a benchpolymer demand, and w hen the rate is mark for performance of dewatering expressed as a dosage rate per tonne of equipment. The characterisation of the dry solids, then the numerical result is a nature of the activated biosolids can therefore be enhanced by a nomination lower figure. of the anticipated non-volatile solids of the dewatered cake. Treatment plants with a high proportion of industrial waste in the influent can produce a higher ash content biosolids cake, and hence a higher solids cake.

In the past, process performance specifications fo r greenfield plants have not been a reasonable method of ensuring adequate equipment due to the unknown nature of the sludge. Ifthe ash content and corresponding cake solids requirements can be specified, the plant owner can determine the level of dewatering that will In December 1996 the Bureau of Meteorology issued an important amendment be achieved, and will be able to choose to Bulletin 53 - The Estimation of Probable Maximum Precipitation in between the standard or high perforAustralia: Generalised Short Duration Method (GSDM). mance equipment.

If a higher solids content than the regression line of Figure 1 is desired, The main amendment changes the recommended method of deriving the design then the new generation of dewatering spatial distribution of the probable maximum precipitation. There are also equipment will be required, but the cost changes to the list of notable point rainfall events in Australia. will be much greater.

ATTENTION DAM OWNERS & DESIGNERS

AMENDMENTS TO BULLETIN 53

The change in the method of design spatial distribution is also relevant to those still using Bulletin 51.

Owners of Bulletin 53 or Bulletin 51 may obtain copies of the amendments, free of charge, from: Bulletin 53 Amendment Hydrometeorological Advisory Service Bureau of Meteorology GPO Box 1289K Melbourne VIC 3001 Phone: (03) 9669 4608 Fax: (03) 9669 4725 email: bulletin53 @bom.gov.au (include postal address) or may download it as a postscript file from: http://www.bom.gov.au/hydro/has/bu1l53.shtml 40

WATER MARCH/ APRI L 199 7

References Bane I H (1990) "Belt Press and Gravity Table D ewatering Process Perfo rmance-Myth and AWWA Qld R egional R eality" Conference Cabarita Lakes.

R etter E A and Schilp R (1994) "Solid Bowl Centrifuges for W astewater Sludge Treatm ent" - Filtration and Separation June (1996) "Pilot Trials at Sernagiotto C.O.R.D .A.R. (Italy) Comparison between BPF WR New Generation Belt Press and Noxon and H umbolt high performance Centrifuges". (Unpub[jshed)

Author Ian Bane is Manager-Environmental Engineering for Supaflo Technologies Pty Ltd, 126 Frenchs Forest R oad, Sydney

WASTEWATER

IDEA Plants in Victoria At the Victorian branch meeting on the intermittently decanted extended aeration (IDEA) process, Go rdon Sewards of Enviroco n Consulting Engineers provided an overview of IDEA. H e also discussed the results from pilot test work carried out at Geelong as part of process design for t he Black Rock plant.

T he new facility was required to meet EPA licence criteria by removing 89% of BOD and 83% of suspended solids. In addition, some ammonia and organic nitrogen was required to be removed, together with some heavy metals.

A pilot plant was built at Black Rock to investigate alternative treat ment processes that included: • conventional activated sludge • nitrifying activated sludge • continuous extended aeration • IDEA • trickling filter-solids contact.

T he pilot work showed that all systems met the EPA licence criteria (except ammo nia- nitrogen i n the conven tional activated sludge process).

Yet the system that appeared to do so

Table 1 Black Rock Sewage Treatment Plant Upgrade-Pilot Plant Results Parameter

EPA Licence

Influent

PIiot Plant Effluent Average (minimum)

340 370 39 22 61

10 (<10) 19 (10) 0.9 (0.06) 4.7 (2.9) 5.5 (3.0) 7.3 (5.6) 12.8 (10.5) 3.4 (0.8)

Median BOD, mg/L SS, mg/L NH3 -N, mg/L Org-N, mg/L TKN, mg/L TON, mg/L TN, mg/L TP, mg/L

40 60 20 20

-

61 8

10

Removal %

97 95 98 79 91

79 58

Table 2 Victorian IDEA Plants-Basic Design Criteria Parameter F/ M RATIO kg BOD/kg MLSS. Detention Time, h MLSS, mg/L Sludge Age, d

Black Rock

Moe

Warrnambool

d0.05 36 5,000 30

0.04 38 3,500 38

0.05 43 4,500

with the most ease and with the least complications (while being the most 'forgiving') was the IDEA process. It was recognised that the IDEA system is energy intensive.

A cost analysis showed that the lowest net p resent value system was the extended aeration process, followed by higher), trickling IDEA (1.2% filter- solids contact (2 1% higher) and nitrifying ac tivated sludge (22%

42

higher).

A summary of Black Rock pilot plant results for the IDEA process is shown in Table 1.

In summary, the reasons for selecting the IDEA process for the Black R ock plant included: • ability to meet EPA licence requirements • ability to cope with shock organic and hydraulic loads

WATER MARCH/APRI L 1997

41

WASTEWATER • reliability, flexibility and robustness • minimal routine operator intervention • stabilised sludge • low odour potential • low net present value (despite being energy intensive).

IDEA systems have also been selected at Warrnambool and Moe. A summary comparison of design criteria is listed in Table 2.

Givytt Williams, Manager Asset Development at Barwon Water, then provided details of the design of the Black Rock IDEA plant and its initial performance.

The original treatment plant at Black Rock served about 175,000 people plus industries. It involved a screening plant with a 0.5 mm opening, grit tanks and a 1.2 km submarine outfall.

The new plant at Black Rock has the following elements: • the existing screening plant, with a new control centre • two aerobic selectors with one hour

detention time • four aerobic tanks, each 120 m x 60 m • a diffused air aeration system with associated plant • sludge thickening and dewatering • a localised reuse scheme using a Memtec microfiltration plant • an automatic plant monitoring and control system.

Some of the key features of the plant design and operation include: • average dry weather flow of70 ML/d (PWWF 210 ML/d) • flow through the selectors is plug flow and aerated to prevent odour generation.

Nutrient removal is currently not a requirement for the Black Rock plant. is contin• flow to the aeration tanks uous throughout all phases of operation (ie. aeration and non-aeration periods) and the tanks are designed so that short circuiting does not occur during decant periods • effluent is decanted from just below the surface by specially designed skimmers and the decant rate is at the capacity rate of the ocean outfall (210 ML/day) • return activated sludge is mixed with incoming sewage to enhance the biological process and discourage the generation of unwanted filamentous bacteria which could lead to foaming or sludge bulking problems • sludge is wasted during the aeration cycles only so as to provide a constant supply at ½% solids to the thickening/dewatering trains • sludge dewatering is by gravity deck followed by belt press, and sludge disposal is to long-term storages on site.

The total project estimateincluding investigations, design, incidental works and overheads-is $42m.

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Sewage was first introduced to the plant in May 1996. No mixed liquor was introduced to the plant from any other treatment facility and the biomass was generated by its own self-seeding.

This process was trialled in the pilot plant and proved successful in both the pilot plant and the full-scale plant.

Preliminary results show very satisfactory performances for BOD and SS removal, even prior to reaching the design MLSS level.

The final presentation was by Trevo,· Kitchin and Frank Hall of Fisher Stewart. They outlined the background and provided details about the design and construction of the Moe waste water plant upgrade.

Trevor described the existing plant and the process of developing the detailed design. The IDEA process was adopted for the upgrade. One part of the process was the use of value management methods which resulted in one of the four original proposed reactor tanks being deferred in initial construction.

Frank outlined some of the construction issues involved in the project, including using precast concrete wall units for the construction of the reactor tanks.

Trade Waste The Annual Trade Waste Seminar was held at the Parramatta Leagues Club on 31 October 1996 with 100 people attending. The day's proceedings involved six speakers, an excellent lunch and a site visit.

Colin Ridley, Manager of Sydney Water's Wastewater Source Control Branch, presented an overview of the Trade Waste Policy and implications of the EPA's pollution reduction targets.

Colin spoke about the Ecological Risk Assessment (ERA) project, which investigated the effects of 114 chemicals in the environment. This found that pesticides from coastal STPs were a small risk to swimmers and that disinfection by-products were a risk from inland STPs. Organo-phosphate pesticides which were detected and determined to be harmful are to have current consents to discharge discontinued and no new consents granted. Other EPA initiatives which will change future Trade Waste ~olicy is the move to load-based licensmg.

Liz Uliana, Manager EMS Certification, NATA, spoke about the background of the ISO-14001, Environmental Management Systems.

Stemming from the outcomes of the Environmental Conference in Rio (1992) a voluntary code called Eco Management and Audit Scheme (EMAS) was adopted by the European Union, which has led to the preparation